arXiv subjects

K. G. Suresh

Publications and source records attributed to K. G. Suresh.

At least 19 recordsLinked to original sources

arXiv2025

Tailoring hard magnetic properties of Fe2MnSn Heusler alloy via interstitial modification: A first-principles approach

We employ first-principles calculations to explore interstitial engineering as a strategy to tailor the hard magnetic properties of Fe2MnSn Heusler alloy, establishing its potential as a rare-earth-free permanent magnet. By introducing light interstitial elements -- B, C, H, N, O, and F -- at varying concentrations (1.56-12.5 at%), we uncover significant enhancements in structural stability, magnetization, Curie temperature, and magnetocrystalline anisotropy. These dopants preferentially occupy octahedral interstitial sites in the hexagonal phase of Fe2MnSn, leading to localized lattice distortions that enhance its magnetic characteristics. Notably, at 12.5 at% doping, B, C, N, and O induce a critical transition from in-plane to out-of-plane magnetic anisotropy -- achieved without 5d or rare-earth elements -- highlighting a sustainable pathway to high-performance magnets. Among these, N-doped Fe2MnSn exhibits the highest uniaxial anisotropy (0.61 MJ/m^3), followed by the B-doped (0.44 MJ/m^3) alloy. The magnetization of the doped compounds surpasses that of conventional ferrites and gap magnets like MnAl and MnBi. The Curie temperature sees a substantial boost, reaching 1058 K for O-doped Fe2MnSn and 1000 K for the C-doped alloy. Although N-doping results in a modest increase in Tc (744 K vs. 729 K for the pristine alloy), it delivers superior hard magnetic properties, with the highest magnetic hardness (0.65) and an enhanced maximum energy product (0.36 MJ/m^3), making it a strong candidate for gap magnet applications. These findings highlight interstitial doping as a viable route to engineer rare-earth-free permanent magnets with optimized magnetic performance.

cond-mat.mtrl-sci↗

arXiv2024

GdAlSi: An antiferromagnetic topological Weyl semimetal with non-relativistic spin splitting

Spintronics has emerged as a viable alternative to traditional electronics based technologies in the past few decades. While on one hand, the discovery of topological phases of matter with protected spin-polarized states has opened up exciting prospects, recent revelation of intriguing non-relativistic spin splitting in collinear antiferromagnetic materials with unique symmetries facilitate a wide possibility of realizing both these features simultaneously. In this work, we report the co-existence of these two intriguing properties within a single material: GdAlSi. It crystallizes in a body-centered tetragonal structure with a non-centrosymmetric space group $I4_{1}md$ ($109$), which is confirmed using detailed structural analysis through X-ray diffraction (XRD) and optical second harmonic generation (SHG) measurements. The magnetization data indicates AFM ordering with an ordering temperature ($T_N$) $\sim$ 32 K. Ab-initio calculations reveal GdAlSi to be a collinear antiferromagnetic Weyl semimetal with an unconventional, momentum-dependent spin splitting, also referred to as altermagnet. Angle-resolved photoemission spectroscopy measurements on GdAlSi single crystals subsequently confirm the presence of Fermi arcs, a distinctive hallmark of Weyl semimetals. Electric and magnetic multipole analysis provides a deeper understanding of the symmetry-mediated, momentum-dependent spin splitting, which has strictly non-relativistic origin. To the best of our knowledge, such co-existence of unconventional antiferromagnetic order and non-trivial topology is unprecedented and has never been observed before in a single material, rendering GdAlSi a special and promising candidate material. We propose a device harnessing these features, poised to enable practical and efficient topotronic applications.

cond-mat.str-el↗

arXiv2023

Spin-valve nature and giant coercivity of a ferrimagnetic spin semimetal Mn$_2$IrGa

Spin semimetals are amongst the most recently discovered new class of spintronic materials, which exhibit a band gap in one spin channel and semimetallic feature in the other, thus facilitating tunable spin transport. Here, we report Mn$_2$IrGa to be a candidate material for spin semimetal along with giant coercivity and spin-valve characteristics using a combined experimental and theoretical study. The alloy crystallizes in an inverse Heusler structure (without any martensitic transition) with a para- to ferri-magnetic transition at $T_\mathrm{C} \sim$ 243 K. It shows a giant coercive field of about 8.5 kOe (at 2 K). The negative temperature coefficient, relatively low magnitude and weak temperture dependance of electrical resistivity suggest the semimetallic character of the alloy. This is further supported by our specific heat measurement. Magnetoresistance (MR) confirms an irreversible nature (with its magnitude $\sim$1\%) along with a change of sign across the magnetic transition indicating the potentiality of Mn$_2$IrGa in magnetic switching applications. In addition, asymmetric nature of MR in the positive and negative field cycles is indicative of spin-valve characteristics. Our ab-initio calculations confirm the inverse Heusler structure with ferrimagnetic ordering to be the lowest energy state, with a saturation magnetization of 2 $μ_\mathrm{B}$. $<100>$ is found to be the easy magnetic axis with considerable magneto-crystalline anisotropy energy. A large positive Berry flux at/around $Γ$ point gives rise to an appreciable anomalous Hall conductivity ($\sim$-180 S/cm).

cond-mat.mtrl-sci↗

arXiv2023

FeRhCrSi: A new spin semimetal with room temperature spin-valve behavior

Spin semimetals are a recently discovered new class of spintronic materials, which exhibit a band gap in one spin channel while a semimetallic feature in the other and thus allows for tunable spin transport. Here, we present experimental verification of spin semimetallic behavior in FeRhCrSi, a quaternary Heusler alloy with saturation moment 2 $μ_B$ and Curie temperature $>$ 400 K. It crystallises in the L2$_1$ structure with 50$\%$ antisite disorder between Fe and Rh. Below 300 K, it shows a weakly temperature dependent electrical resistivity with negative temperature coefficient, indicating the normal semimetal or spin semimetal behavior. Anomalous magnetoresistance data reveals dominant contribution from asymmetric part, a clear signature of spin-valve nature, which is retained even at room temperature. \textcolor{black}{The asymmetric part of magneto-resistance shows an unusual increase with increasing temperature.} Hall measurements confirm the anomalous nature of conductivity originating from the intrinsic Berry curvature, with holes being the majority carriers. Ab-initio simulation confirms a unique long-range ferrimagnetic ordering to be the ground state, explaining the origin behind the unexpected low saturation moment. The ferrimagnetic disordered structure confirms the spin semimetallic feature of FeRhCrSi, as observed experimentally.

cond-mat.mtrl-sci↗

arXiv2023

CoRuVSi: A potential candidate for spin semimetal with promising spintronic and thermoelectric properties

Based on our experimental and theoretical studies, we report the identification of the quaternary Heusler alloy, CoRuVSi as a new member of the recently discovered spin semimetals class. Spin polarised semimetals possess a unique band structure in which one of the spin bands shows semimetallic nature, while the other shows semiconducting/insulating nature. Our findings show that CoRuVSi possesses interesting spintronic and thermoelectric properties. Magnetization data reveal a weak ferri-/antiferro magnetic ordering at low temperatures, with only a very small moment $\sim$ 0.13 $μ_B$/f.u., attributed to the disorder. Transport results provide strong evidence of semimetallicity dominated by two-band conduction, while magnetoresistance data show a non-saturating, linear, positive, magnetoresistance. Spin polarization measurements using point-contact Andreev reflection spectra reveal a reasonably high spin polarization of $\sim$ 50\%, which matches fairly well with the simulated result. Furthermore, CoRuVSi shows a high thermopower value of $0.7$ $m Watt/ m-K^{2}$ at room temperature with the dominant contribution from the semimetallic bands, rendering it as a promising thermoelectric material as well. Our ab-initio simulation not only confirms a unique semimetallic feature, but also reveals that the band structure hosts a linear band crossing at $\sim$ -0.4 eV below the Fermi level incorporated by a band-inversion. In addition, the observed topological non-trivial features of the band structure is corroborated with the simulated Berry curvature, intrinsic anomalous Hall conductivity and the Fermi surface. The coexistence of many interesting properties relevant for spintronic, topological and thermoelectric applications in a single material is extremely rare and hence this study could promote a similar strategy to identify other potential materials belonging to same class.

physics.app-ph↗

arXiv2022

Griffiths' phase behavior of the Weyl semimetal CrFeVGa

We report a combined theoretical and experimental study of a new topological semimetal CrFeVGa with an emphasis on the role of atomic disorder on the magnetoelectronic properties and its applications.CrFeVGa belongs to the quaternary Heusler alloy family and crystallizes in the cubic structure. Synchrotron XRD measurement confirms B2 disorder, which plays a crucial role in dictating the electronic and magnetic properties of the system.

cond-mat.str-el↗

arXiv2022

Disorder-mediated quenching of magnetization in NbVTiAl: Theory and Experiment

In this paper, we present the structural, electronic, magnetic and transport properties of a equiatomic quaternary alloy NbVTiAl. The absence of (111) and (200) peaks in X-ray diffraction (XRD) data confirms the A2-type structure. Magnetization measurements indicate a high Curie temperature and a negligibly small magnetic moment ($\sim 10^{-3} μ_B/f.u.$) These observations are indicative of fully compensated ferrimagnetism in the alloy. Temperature-dependent resistivity indicates metallic nature. Ab-initio calculation of fully ordered NbVTiAl structure confirms a nearly half metallic behavior with a high spin polarization ($\sim$ 90 \%) and a net magnetic moment of 0.8 $μ_B/f.u.$ (in complete contrast to the experimental observation). One of the main objective of the present paper is to resolve and explain the long-standing discrepancy between theoretical prediction and experimental observation of magnetization for V-based quaternary Heusler alloys, in general. To gain an in-depth understanding, we modelled various disordered states and its subsequent effect on the magnetic and electronic properties. The discrepancy is attributed to the A2 disorder present in the system, as confirmed by our XRD data. The presence of disorder also causes the emergence of finite states at the Fermi level, which impacts the spin polarization of the system.

cond-mat.mtrl-sci↗

arXiv2021

CoFeVSb: A Promising Candidate for Spin Valve and Thermoelectric Applications

We report a combined theoretical and experimental study of a novel quaternary Heusler system CoFeVSb from the view point of room temperature spintronics and thermoelectric applications. It crystallizes in cubic structure with small DO$_3$-type disorder. The presence of disorder is confirmed by room temperature synchrotron X-ray diffraction(XRD) and extended X-ray absorption fine structure (EXAFS) measurements. Magnetization data reveal high ordering temperature with a saturation magnetization of 2.2 $μ_B$/f.u. Resistivity measurements reflect half-metallic nature. Double hysteresis loop along with asymmetry in the magnetoresistance(MR) data reveals room temperature spin-valve feature, which remains stable even at 300 K. Hall measurements show anomalous behavior with significant contribution from intrinsic Berry phase. This compound also large room temperature power factor ($\sim0.62$ mWatt/m/K$^{2}$) and ultra low lattice thermal conductivity ($\sim0.4$ W/m/K), making it a promising candidate for thermoelectric application. Ab-initio calculations suggest weak half-metallic behavior and reduced magnetization (in agreement with experiment) in presence of DO$_3$ disorder. We have also found an energetically competing ferromagnetic FM)/antiferromagnetic (AFM) interface structure within an otherwise FM matrix: one of the prerequisites for spin valve behavior. Coexistence of so many promising features in a single system is rare, and hence CoFeVSb gives a fertile platform to explore numerous applications in future.

cond-mat.mtrl-sci↗

arXiv2021

Colossal Anomalous Hall Conductivity and Topological Hall Effect in Ferromagnetic Kagome Metal Nd$_3$Al

Historically, the genesis of anomalous Hall effect (AHE) in magnetic materials has always been a fascinating yet controversial topic in the solid state physics community. Recent progress on the understanding of this topic has revealed an intimate connection between the Berry curvature of occupied electronic states and the intrinsic AHE. Magnetic Weyl semimetals with broken time reversal symmetry is a classic example, which is expected to show large contributions to Berry curvature around the topological nodes and hence to the AHE. Here, we report a kagome metallic ferromagnet Nd$_3$Al, with a large unconventional positive magnetoresistance (~ 80 %) and colossal anomalous Hall conductivity of 1.8x10^5 S/cm (largest ever reported to the best of our knowledge). We also show that the magnetic state of this compound is quite different from its analogues in many respects. While the compound is predominantly an itinerant ferromagnet, its low temperature phase exhibits topological band structure, enhanced skew scattering as well as topological spin texture arising in the spin frustrated kagome lattice. Various experimental findings such as topological Hall effect, non-saturating positive magnetoresistance etc. give strong indication to this scenario. Ab-initio calculations broadly confirm the experimental findings by revealing the presence of flat bands and Weyl points originating from the itinerant Nd moments. The non-trivial band structure, enhanced skew scattering and the spin texture in a clean polycrystalline sample are found be responsible for the colossal Hall conductivity and topological Hall effect.

cond-mat.str-el↗

arXiv2021

High T$_C$ ferromagnetic inverse Heusler alloys: A comparative study of Fe$_2$RhSi and Fe$_2$RhGe

We report the results of experimental investigations on structural, magnetic, resistivity, caloric properties of Fe$_2$RhZ (Z=Si,Ge) along with \textit{ab-initio} band structure calculations using first principle simulations. Both these alloys are found to crystallize in inverse Heusler structure but with disorder in tetrahedral sites between Fe and Rh. Fe$_2$RhSi has saturation moment of 5.00 $μ_B$ and while its counterpart has 5.19 $μ_B$. Resistivity measurement reveals metallic nature in both of them. Theoretical simulations using generalized gradient approximation(GGA) predict inverse Heusler structure with ferromagnetic ordering as ground state for both the alloys. However it underestimates the experimentally observed moments. GGA+$U$ approach, with Hubbard $U$ values estimated from density functional perturbation theory helps to improve the comparison of the experimental results. Fe$_2$RhSi is found to be half metallic ferromagnet while Fe$_2$RhGe is not. Varying $U$ values on Fe and Rh sites does not change the net moment much in Fe$_2$RhSi, unlike in Fe$_2$RhGe. Relatively small exchange splitting of orbitals in Fe$_2$RhGe compared to that of Fe$_2$RhSi is the reason for not opening the band gap in the minority spin channel in the former. High ordering temperature and moment make Fe$_2$RhSi useful for spintronics applications.

cond-mat.mtrl-sci↗

arXiv2020

Bipolar Magnetic Semiconducting Behavior in VNbRuAl: A New Spintronic Material for Spin Filters

We report the theoretical prediction of a new class of spintronic materials, namely bipolar magnetic semiconductor (BMS), which is also supported by our experimental data. BMS acquires a unique band structure with unequal band gaps for spin up and down channels, and thus are useful for tunable spin transport based applications such as spin filters. The valence band (VB) and conduction band (CB) in BMS approach the Fermi level through opposite spin channels, and hence facilitate to achieve reversible spin polarization which are controllable via applied gate voltage. We report the quaternary Heusler alloy VNbRuAl to exactly possess the band structure of BMS. The alloy is found to crystallize in LiMgPdSn prototype structure (space group $F\bar{4}3m$) with B$2$ disorder and lattice parameter 6.15 Å. The resistivity and Hall measurements show a two channel semiconducting behavior and a quasi linear dependence of negative magneto resistance (MR) indicating the possible semiconducting nature. Interestingly, VNbRuAl also shows a fully compensated ferrimagnetic (FCF) behavior with vanishing net magnetization (m$_s$$\sim$ $10^{-3}$ $μ_B/f.u.$) and significantly high ordering temperature ($> 900$ K). Unlike conventional FCF, vanishing moment in this case appears to be the result of a combination of long range antiferromagnetic (AFM) ordering and the inherent B2 disorder of the crystal. This study opens up the possibility of finding a class of materials for AFM spintronics, with great significance both from fundamental and applied fronts.

physics.app-ph↗

arXiv2019

Half-metallic ferromagnetism and Ru-induced localization in quaternary Heusler alloy CoRuMnSi

We report a combined theoretical and experimental investigation of half-metallic ferromagnetism in equiatomic quaternary Heusler alloy CoRuMnSi. Room temperature XRD analysis reveals that the alloy crystallizes in L21 disorder instead of pristine Y-type structure due to 50% swap disorder between the tetrahedral sites, i.e., Co and Ru atoms. Magnetization measurements reveal a net magnetization of 4 $μ_B$ with Curie temperature of ~780 K. Resistivity measurement reveals the presence of localization effect below 35 K while above 100 K, a linear dependence is observed. Resistivity behavior indicates the absence of single magnon scattering, which indirectly supports the half-metallic nature. The majority spin band near the Fermi level clearly indicates the overlap of flat eg bands with sharply varying conduction bands that are responsible for the localization. In-depth analysis of the projected atomic d-orbital character of band structure reveals unusual bonding, giving rise to the flat eg bands purely arising out of Ru ions. Co-Ru swap disorder calculations indicate the robustness of half-metallic nature, even when the structure changes from Y-type to L21-type, with no major change in the net magnetization of the system. Thus, robust half-metallic nature, stable structure, and high Curie temperature make this alloy quite a promising candidate to be used as a source of highly spin-polarized currents in spintronic applications.

cond-mat.mtrl-sci↗

arXiv2019

Experimental and Theoretical Investigation on the Possible Half-metallic Behaviour of Equiatomic Quaternary Heusler Alloys: CoRuMnGe and CoRuVZ (Z = Al, Ga)

In this report, structural, electronic, magnetic and transport properties of quaternary Heusler alloys CoRuMnGe and CoRuVZ (Z = Al, Ga) are investigated. All the three alloys are found to crystallize in cubic structure. CoRuMnGe exhibits L2$_1$ structure whereas, the other two alloys have B2-type disorder. For CoRuMnGe and CoRuVGa, the experimental magnetic moments are in close agreement with the theory as well as those predicted by the Slater-Pauling rule, while for CoRuVAl, a relatively large deviation is seen. The reduction in the moment in case of CoRuVAl possibly arises due to the anti-site disorder between Co and Ru sites as well as V and Al sites. Among these alloys, CoRuMnGe has the highest T$\mathrm{_C}$ of 560 K. Resistivity variation with temperature reflects the half-metallic nature in CoRuMnGe alloy. CoRuVAl shows metallic character in both paramagnetic and ferromagnetic states, whereas the temperature dependence of resistivity for CoRuVGa is quite unusual. In the last system, $ρ$ vs. T curve shows an anomaly in the form of a maximum and a region of negative temperature coefficient of resistivity (TCR) in the magnetically ordered state. The ab initio calculations predict nearly half-metallic ferromagnetic state with high spin polarization of 91, 89 and 93 \% for CoRuMnGe, CoRuVAl and CoRuVGa respectively. To investigate the electronic properties of the experimentally observed structure, the Co-Ru swap disordered structures of CoRuMnGe alloy are also simulated and it is found that the disordered structures retain half-metallic nature, high spin polarization with almost same magnetic moment as in the ideal structure. Nearly half-metallic character, high T$\mathrm{_C}$ and high spin polarization make CoRuMnGe alloy promising for room temperature spintronic applications.

cond-mat.mtrl-sci↗

arXiv2019

Co-existence of spin semi-metallic and Weyl semi-metallic behavior in FeRhCrGe

In this letter, we report the discovery of a new class of spintronic materials, namely spin semi-metals (SSM), employing both theoretical and experimental tools. The band structure of this class of materials is such that one of the spin bands resembles that of a semi-metal, while the other is similar to that of an insulator/semiconductor. This report is the experimental verification of the first SSM, FeRhCrGe, a quaternary Heusler alloy with a magnetic moment 3 $μ_B$ and a Curie temperature of 550 K. The measurement below 300 K shows nearly temperature independent conductivity and a relatively moderate Hall effect. SSM behavior for FeRhCrGe is also confirmed by rigorous first principles calculations. Band structure calculations also reveal that the spin up (semi metallic) band has combined features of type II Weyl and nodal line semimetal. As such, this study opens up the possibility of a new class of material with combined spintronic and topological properties, which is important both from fundamental and applied point of view.

cond-mat.mtrl-sci↗

arXiv2018

Spin Gapless Semiconducting Nature in Co-rich Co1+xFe1-xCrGa: Insight and Advancements

In this report, we present structural, electronic, magnetic and transport properties of Co-rich spin gapless semiconductor CoFeCrGa using both theoretical and experimental techniques. The key advantage of Co-rich samples $\mathrm{Co_{1+x}Fe_{1-x}CrGa}$ is the high Curie temperature (T$\mathrm{_C}$) and magnetization, without compromising the SGS nature (up to x = 0.4), and hence our choice. The quaternary Heusler alloys $\mathrm{Co_{1+x}Fe_{1-x}CrGa}$ (x = 0.1 to 0.5) are found to crystallize in LiMgPdSn-type structure having space group $F\bar{4}3m$ (\# 216). The measured Curie temperature increases from 690 K (x = 0) to 870 K (x = 0.5). Observed magnetization values follow the Slater-Pauling rule. Measured electrical resistivity, in the temperature range of 5-350 K, suggests that the alloys retain the SGS behavior up to x = 0.4, beyond which it reflects metallic character. Unlike conventional semiconductors, the conductivity value ($\mathrm{σ_{xx}}$) at 300 K lies in the range of 2289 S $\mathrm{cm^{-1}}$ to 3294 S $\mathrm{cm^{-1}}$, which is close to that of other reported SGS materials. The anomalous Hall effect is comparatively low. The intrinsic contribution to the anomalous Hall conductivity increase with x, which can be correlated with the enhancement in chemical order. The anomalous Hall coefficient is found to increase from 38 S/cm for x = 0.1 to 43 S/cm for 0.3. Seebeck coefficients turn out to be vanishingly small below 300 K, another signature for being SGS. All the alloys (for different x) are found to be both chemically and thermally stable. Simulated magnetization agrees fairly with the experiment. As such Co-rich CoFeCrGa is a promising candidate for room temperature spintronic applications, with enhanced T$\mathrm{_C}$, magnetic properties and SGS nature.

cond-mat.mtrl-sci↗

arXiv2018

$\mathrm{Co_2Fe_{1-x}Cr_xSi}$ Heusler Alloys : A promising material for spintronics application

In this article, we investigated the effect of Cr substitution in place of Fe on the structural, magnetic and transport properties of $\mathrm{Co_2FeSi}$ alloy. A comprehensive structural analysis is done using X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy. Quaternary Heusler compounds $\mathrm{Co_2Fe_{1-x}Cr_xSi}$ with Cr content (x = 0.1, 0.3, 0.5) were found to crystallize in cubic structure. The synchrotron based EXAFS studies reveal that the anti-site disorder increases with the increase in Cr concentration. The saturation magnetization values in all the alloys are found to be less than those expected from the Slater-Pauling rule, which may be due to the some inherent disorder. A detailed resistivity analysis in the temperature range of 5-300 K is done, taking into account different scattering mechanisms. The residual resistivity ratio is found to decrease with increasing Cr concentration. A disorder induced resistivity minimum due to weak localization effect is seen for x = 0.5. The resistivity measurements also indicate that the half-metallic character survives upto 100 K for x = 0.1, whereas the alloys with x= 0.3 and 0.5 show signature of half- metallic nature even at higher temperatures. First principles calculation done with a more robust exchange correlation functional (namely HSE-06) confirms the half metallicity in the entire concentration range. Theoretically simulated band gap and magnetic moments compliment the experimental findings and are compared wherever possible. All these properties make $\mathrm{Co_2Fe_{1-x}Cr_xSi}$ a promising material for spintronics application.

cond-mat.mtrl-sci↗

arXiv2017

Magnetic phase separation and strong AFM nature of hexagonal Gd$_5$Sb$_3$

We report on the combined results of structural, magnetic, transport and calorimetric properties of Mn$_5$Si$_3$-type hexagonal Gd$_5$Sb$_3$. With decreasing temperature, it exhibits a ferromagnetic-like transition at 265 K, Néel transition at 95.5 K and a spin-orientation transition at 62 K. The system is found to be in AFM state down to 2 K in a field of 70 kOe. Magnetic phase coexistence is not noticeable despite large positive Curie-Weiss temperature. Instead low-temperature AFM and high-temperature FM-like phases are separated in large temperature. Temperature-magnetic field ($H$-$T$) phase diagram reveals field-driven complex magnetic phases. Within the AFM phase, the system is observed to undergo field-driven spin-orientation transitions. Field-induced tricritical and quantum critical points appear to be absent due to strong AFM nature and by the intervention of FM-like state between PM and AFM states. Electrical resistivity along with large Sommerfeld parameter suggests metallic nature.

cond-mat.mtrl-sci↗

arXiv2017

Competing magnetic and spin gap-less semiconducting behaviour in fully compensated ferrimagnet CrVTiAl: Theory and Experiment

We report the structural, magnetic and transport properties of polycrystalline CrVTiAl alloy along with first principles calculations. It crystallizes in the LiMgPdSn type structure with lattice parameter 6.14 Å at room temperature. Absence of (111) peak along with the presence of a weak (200) peak indicates the antisite disorder of Al with Cr and V atoms. The magnetization measurements reveal a ferrimagnetic transition near 710 K and a coercive field of 100 Oe at 3 K. Very low moment and coercive field indicate fully compensated ferrimagnetism in the alloy. Temperature coefficient of resistivity is found to be negative, indicating a characteristic of semiconducting nature. Absence of exponential dependence of resistivity on temperature indicates a gapless/spin-gapless semiconducting behaviour. Electronic and magnetic properties of CrVTiAl for three possible crystallograpic configurations are studied theoretically. All the three configurations are found to be different forms of semiconductors. Ground state configuration is a fully compensated ferrimagnet with band gaps 0.58 eV and 0.30 eV for up and down spin bands respectively. The next higher energy configuration is also ferrimagnetic, but has spin-gapless semiconducting nature. The highest energy configuration corresponds to a non-magnetic gapless semiconductor. The energy differences among these configurations are quite small ($<$ 1 $\mathrm{mRy/atom}$) which hints that at finite temperatures, the alloy exists in a disordered phase, which is a mixture of the three configurations. By taking into account the theoretical and the experimental findings, we conclude that CrVTiAl is a fully compensated ferrimagnet with predominantly spin gap-less semiconductor nature.

cond-mat.mtrl-sci↗