arXiv subjects

V. N. Krasnorussky

Publications and source records attributed to V. N. Krasnorussky.

11 recordsLinked to original sources

arXiv2026

The New High-entropy Compound RhMnFeCoGe4 with Cubic Non-centrosymmetric B20 Structure

A novel high-entropy compound, RhMnFeCoGe$_4$, with a cubic non-centrosymmetric B20 struc- ture, has been synthesized under conditions of high pressure and temperature. The electrical transport and magnetic properties of the obtained compound at both ambient and elevated pres- sures have been investigated. In addition, nuclear magnetic resonance (NMR) spectra were obtained at 4.2 K and ab initio calculations were performed. The new material exhibits ferromag- netic behavior with a critical temperature of $T_C$ = 146 K and a spontaneous moment of 2.5 $μ_B$ per formula unit. The magnetization data obtained at the critical region yielded the critical temperature and exponents, which were found to be $T_C$ = 146(1) K, $β$ = 0.337(1), $γ$ = 1.121(1), and $δ$ = 4.326(1). The magnetic moments of Mn and Co were determined from NMR spectra to be 2.2 $μ_B$ and 0.5 $μ_B$, respectively. Ab initio calculations yielded reasonable values for the lattice parameter and the magnetic moments of all constituents. The density of states and band structure are determined for both paramagnetic and ferromagnetic states. Lattice compression results in the increase in the $T_C$.

cond-mat.mtrl-sci↗

arXiv2026

SANS and magnetometry study of the magnetic phase diagram of the B20 helimagnet FeRhSi

This manuscript reports the first direct neutron-scattering evidence for long-period helimagnetism in the newly identified 4d-substituted B20 compound Fe0.5Rh0.5Si. By combining SANS with low-field magnetometry, we establish the magnetic modulation, construct a field-temperature phase diagram, and identify a candidate A-phase region supported by an independent structural signature. The work is important beyond this single compound because it expands the family of chiral B20 helimagnets into Rh-substituted materials, where spin-orbit coupling, disorder, and Dzyaloshinskii-Moriya interactions can be tuned. It will interest researchers in chiral magnetism, topological spin textures, magnetic neutron scattering, and quantum materials, and provides a foundation for future studies of emergent magnetic phases and topology-driven phenomena in chemically tuned chiral magnets.

cond-mat.str-el↗

arXiv2024

Evidence for spin droplets (ferrons) formation in the heavy fermion metal CeB$_6$ with dynamic charge stripes

The presented studies of resistivity (R), thermal conductivity (k) and specific heat (C) at low temperature 1.8-7 K in magnetic field up to 90 kOe made it possible to detect for the first time the exponential field dependences R(H), 1/k(H), $C(H) \sim \exp(-μ_{\rm eff}H/kBT)$ of the charge transport and thermal characteristics in the so-called antiferroquadrupole (AFQ) phase of the archetypal heavy-fermion CeB$_6$ hexaboride. From magnetoresistance measurements it is shown that in the AFQ state the effective magnetic moment varies in the range $μ_{\rm eff}(T) = 1.4$-1.9$μ$B, and its value is very close to $μ_{\rm eff}(τ)(T) = 2μ$B, derived from the field dependence of the relaxation time $|tau(H)$ observed in the heat capacity and thermal conductivity experiments. The phenomenological model proposed here allowed us to attribute the magnetic moments to spin droplets (ferrons), that appear in the bulk AFQ phase of CeB$_6$ crystals. The relevant electron phase separation at the nanoscale, manifested by dynamic charge stripes, that leads to the formation of ferrons, was revealed from the analysis of low-temperature X-ray diffraction experiments using the maximum entropy method. We argue that the Jahn-Teller collective mode of B$_6$ clusters is responsible for the charge stripe formation, which subsequently induces transverse quasi-local vibrations of Ce ions in the form of pairs and triples. These lead to 4f-5d spin fluctuations providing spin-polarons (ferrons) in the CeB$_6$ matrix.

cond-mat.str-el↗

arXiv2023

Magnetocaloric effect in the high-temperature antiferromagnet YbCoC2

The magnetic $H$-$T$ phase diagram and magnetocaloric effect in the recently discovered high-temperature heavy-fermion compound YbCoC$_2$ have been studied. With the increase in the external magnetic field YbCoC$_2$ experiences the metamagnetic transition and then transition to the ferromagnetic state. The dependencies of magnetic entropy change -$ΔS_m (T)$ have segments with positive and negative magnetocaloric effects for $ΔH \leq 6$~T. For $ΔH = 9$~T magnetocaloric effect becomes positive with a maximum value of -$ΔS_m (T)$ is 4.1 J / kg K and a refrigerant capacity is 56.6 J / kg.

cond-mat.str-el↗

arXiv2022

Hall effect anisotropy in the paramagnetic phase of Ho0.8Lu0.2B12 induced by dynamic charge stripes

A detailed study of charge transport in the paramagnetic phase of Ho0.8Lu0.2B12 strongly correlated antiferromagnet was carried out at temperatures 1.9-300 K in magnetic fields up to 80 kOe. Four mono-domain single crystals with different orientation of normal vectors to the lateral surface of Ho0.8Lu0.2B12 samples were investigated in order to establish the changes in Hall effect due to the anisotropy, induced by (i) the electronic phase separation (dynamic charge stripes) and (ii) formation of the disordered cage-glass state below 60 K. It was demonstrated that in magnetic fields above 40 kOe directed along the 001 and 110 axes in fcc crystals a considerable intrinsic anisotropic positive component Ranxy appears in addition to the ordinary negative Hall resistivity contribution. The relation Ranxy prop. Ranxx 1.7 was found between anomalous components of the resistivity tensor for H along 001 below 60 K, and the power law Ranxy prop. Ranxx 0.83 was detected for the orientation H along 110 at temperatures T below TS about 15 K. It is argued that below TS about 15 K the anomalous odd Ranxy(T) and even Ranxx(T) parts of the resistivity tensor may be interpreted in terms of formation of a large size clusters in the filamentary structure of fluctuating charges (stripes). We assume that these Ranxy(001) and Ranxy(110) components represent the intrinsic (Berry phase contribution) and extrinsic (skew scattering) mechanism, respectively. An additional ferromagnetic contribution to anomalous Hall effect (AHE) for both ordinary and anisotropic components in Hall signal was registered and attributed to the effect of magnetic polarization of 5d states (ferromagnetic nano-domains) in the conduction band of Ho0.8Lu0.2B12.

cond-mat.str-el↗

arXiv2019

Maltese Cross anisotropy in Ho0.8Lu0.2B12 antiferromagnetic metal with dynamic charge stripes

The model strongly correlated electron system Ho0.8Lu0.2B12 which demonstrates a cooperative Jahn-Teller instability of the boron sub-lattice in combination with rattling modes of Ho(Lu) ions, dynamic charge stripes and unusual antiferromagnetic (AF) ground state has been studied in detail at low temperatures by magnetoresistance, magnetization and heat capacity measurements. Based on received results it turns out that the angular H-fi-T magnetic phase diagrams of this non-equilibrium AF metal can be reconstructed in the form of a Maltese cross. The dramatic AF ground state symmetry lowering of this dodecaboride with fcc crystal structure can be attributed to the redistribution of conduction electrons which leave the RKKY oscillations of the electron spin density to participate in the dynamic charge stripes providing with extraordinary changes in the indirect exchange interaction between magnetic moments of Ho3+ ions and resulting in the emergence of a number of various magnetic phases. It is also shown that the two main contributions to magnetoresistance in the complex AF phase, the (i) positive linear on magnetic field and the (ii) negative quadratic component can be separated and analyzed quantitatively, correspondingly, in terms of charge carrier scattering on spin density wave (5d) component of the magnetic structure and on local 4f-5d spin fluctuations of holmium sites.

cond-mat.str-el↗

arXiv2015

Magnetic Single Domain State of the Monochiral Helimagnet MnSi in Zero Field Limit: Magnetic Properties Study

Attention is drawn to a possibility to obtain the monochiral helimagnet MnSi in a magnetic single domain state (SDS) in zero magnetic field limit. It is shown that this metastable zero field magnetic SDS can be achieved by gradual decrease of the field down to zero after initial transformation of MnSi to a spin-polarized state in high fields $H$. This can be achieved only for $\bf{H}\parallel$ [111]. Investigations of MnSi in magnetic SDS give us a possibility to determine the two components of low field magnetic susceptibility of this compound, $χ_{\perp}(T)$ and $χ_{\parallel}(T)$ [$χ_{\perp}$ and $χ_{\parallel}$ correspond to $\bf{H}\perp$, and $\bf{H}\parallel$ (111)-plane containing magnetic moments in helically ordered state]. These results are compared with macroscopic magnetic susceptibility of MnSi earlier determined for this compound only in magnetic multi domain state (MDS). In addition our results are compared with the data reported for some non-monochiral helimagnets. Characteristic features of monochiral helimagnets are elucidated.

cond-mat.str-el↗

arXiv2014

Charge transport in Ho$_x$Lu$_{1-x}$B$_{12}$: Separating Positive and Negative Magnetoresistance in Metals with Magnetic Ions

The magnetoresistance (MR) $Δρ/ρ$ of cage-glass compound Ho$_x$Lu$_{1-x}$B$_{12}$ with various concentration of magnetic holmium ions ($x$$\leq$0.5) has been studied in detail concurrently with magnetization M(T) and Hall effect investigations on high quality single crystals at temperatures 1.9-120 K and in magnetic field up to 80 kOe. The undertaken analysis of $Δρ/ρ$ allows us to conclude that the large negative magnetoresistance (nMR) observed in vicinity of Neel temperature is caused by scattering of charge carriers on magnetic clusters of Ho$^{3+}$ ions, and that these nanosize regions with AF exchange inside may be considered as short range order AF domains. It was shown that the Yosida relation $-Δρ/ρ$$\sim$$M^2$ provides an adequate description of the nMR effect for the case of Langevin type behavior of magnetization. Moreover, a reduction of Ho-ion effective magnetic moments in the range 3-9$μ_B$ was found to develop both with temperature lowering and under the increase of holmium content. A phenomenological description of the large positive quadratic contribution $Δρ/ρ$$\sim$$μ_D^2 H^2$ which dominates in Ho$_x$Lu$_{1-x}$B$_{12}$ in the intermediate temperature range 20-120 K allows to estimate the drift mobility exponential changes $μ_D$$\sim$$T^{-a}$ with $a$=1.3-1.6 depending on Ho concentration. An even more comprehensive behavior of magnetoresistance has been found in the AF state of Ho$_x$Lu$_{1-x}$B$_{12}$ where an additional linear positive component was observed and attributed to charge carriers scattering on the spin density wave (SDW). High precision measurements of $Δρ/ρ=f(H,T)$ have allowed us also to reconstruct the magnetic H-T phase diagram of Ho$_{0.5}$Lu$_{0.5}$B$_{12}$ and to resolve its magnetic structure as a superposition of 4f (based on localized moments) and 5d (based on SDW) components.

cond-mat.str-el↗

arXiv2014

Specific Features of Magnetic Phase Diagram of an MnSi Helimagnet

Magnetization curves of MnSi single crystals have been measured in a range of temperatures $T = 5.5 - 35$ K and magnetic field strengths $H \leq 11$ kOe for $H \parallel$ [111], [001], and [110]. Special attention has been paid to the temperature interval near $T_N = 28.8$K, where MnSi exhibits a transition to the state with a long-period helical magnetic structure. Some new features in the magnetic behavior of MnSi have been found. In particular, in an intermediate temperature region above the transition (28.8 K $= T_N \leq T < 31.5$ K), the $dM(H)/dH$ curves exhibit anomalies that are not characteristic of the typical paramagnetic state. It is established that the line of the characteristic field $H^ \ast (T)$ of this anomaly is a natural extrapolation of the temperature dependence of the field of the transition from a conical phase to an induced ferromagnetic phase observed at $T < T_N$. It is concluded that the properties of MnSi in the indicated intermediate region are related to and governed by those of the conical phase (rather than of the A phase). Based on these data, magnetic phase diagrams of MnSi for $H \parallel$ [111], [001], and [110] are plotted and compared to diagrams obtained earlier by other methods.

cond-mat.str-el↗

arXiv2014

Studying the Magnetic Properties of CoSi Single Crystals

The magnetic properties of CoSi single crystals have been measured in a range of temperatures $T = 5.5 - 450$ K and magnetic field strengths $H \leq 11$ kOe. A comparison of the results for crystals grown in various laboratories allowed the temperature dependence of magnetic susceptibility $χ(T) = M(T)/H$ to be determined for a hypothetical "ideal" (free of magnetic impurities and defects) CoSi crystal. The susceptibility of this ideal crystal in the entire temperature range exhibits a diamagnetic character. The $χ(T)$ value significantly increases in absolute value with decreasing temperature and exhibits saturation at the lowest temperatures studied. For real CoSi crystals of four types, paramagnetic contributions to the susceptibility have been evaluated and nonlinear (with respect to the field) contributions to the magnetization have been separated and taken into account in the calculations of $χ(T)$.

cond-mat.str-el↗

arXiv2014

Magnetization scaling in the paramagnetic phase of Mn1-xFexSi solid solutions

The magnetization field and temperature dependences in the paramagnetic phase of Mn1-xFexSi solid solutions with x<0.3 are investigated in the range B<5 T and T<60 K. It is found that field dependences of the magnetization M(B,T=const) exhibit scaling behavior of the form B\partial M/\partial B-M=F(B/(T-Ts)), where Ts denotes an empirically determined temperature of the transition into the magnetic phase with fluctuation driven short-range magnetic order and F(\c{hi}) is a universal scaling function for given composition. The scaling relation allowed concluding that the magnetization in the paramagnetic phase of Mn1-xFexSi is represented by the sum of two terms. The first term is saturated by the scaling variable \c{hi}=B/(T-Ts), whereas the second is linearly dependent on the magnetic field. A simple analytical formula describing the magnetization is derived and applied to estimates of the parameters characterizing localized magnetic moments in the studied system. The obtained data may be qualitatively interpreted assuming magnetic inhomogeneity of the paramagnetic phase on the nanoscale.

cond-mat.str-el↗