arXiv subjects

Shane Stadler

Publications and source records attributed to Shane Stadler.

6 recordsLinked to original sources

arXiv2024

Structural and magnetic properties of CoTeMoO$_6$ revisited

We have conducted a comprehensive investigation into the magnetic properties of the chiral multiferroic material CoTeMoO$_6$. In contrast with the previous claim of canted antiferromagnetic order with ferromagnetic components, our investigation reveals an antiferromagnetic ground state with compensated moments, providing an interesting platform for exploring exotic material properties. Through careful measurements of magnetization under a series of applied field, we demonstrate that there exist two sequential field-induced magnetic transitions in CoTeMoO$_6$, with one occurring at $H_{c1}$=460 Oe along the a-axis, and the other at $H_{c2}$=1.16 T with the field along the b-axis. The values of $H_{c1}$ and $H_{c2}$ exhibit strong angular dependence and diverge with different rates as the applied field is rotated 90 degrees within the ab plane. This reflects the distinct nature of these transitions, which is further supported by the different critical behavior of $H_{c1}$ and $H_{c2}$, characterized by the values of $\gamma$,in the function of $H_c=H_0\times(1-\frac{T}{T_c})^n$. Furthermore, we have demonstrated that there exist structural and magnetic twin domains in CoTeMoO$_6$ that strongly affect the experimental measurement of their macroscopic properties. Intriguingly, these twin domains can be related to the orthorhombicity/chirality of the crystal structure with the space group $P2_1 2_1 2$. We further explored the magnetic and structural domains with uniaxial pressure and polarized light microscopy. Our results suggest that CoTeMoO$_6$ could be used as a unique platform for investigating the intriguing physics involving intertwined degrees of freedom. The tunability of the underlying domain distribution and its strong anisotropy could also be useful for developing functional devices and applications.

cond-mat.mtrl-sci↗

arXiv2019

Structure-Property Relationship in Layered BaMn2Sb2 and Ba2Mn3Sb2O2

Layered transition-metal compounds have received great attention owing to their novel physical properties. Here, we present the structural, electronic, thermal, and magnetic properties of BaMn2Sb2 and Ba2Mn3Sb2O2 single crystals, both with the layered structure analogous to high-temperature superconductors. While the Mn moment in the MnSb4 tetrahedral environment forms G-type antiferromagnetic (AFM) ordering in both BaMn2Sb2 (TN1~443 K) and Ba2Mn3Sb2O2 (TN1~314 K), a short-range AFM order is found in the intercalated MnO2 layer at a much lower temperature (TN2~60 K) in Ba2Mn3Sb2O2. The directions of the ordered moments in these two magnetic sub-lattices of Ba2Mn3Sb2O2 are perpendicular to each other, even though the system is electrically conductive. This indicates that the large magnetic moments in these compounds are highly localized, leading to negligible coupling between MnSb4 and MnO2 layers in Ba2Mn3Sb2O2. These findings provide an insight into the structure-magnetism-based design principle for new superconductors.

cond-mat.str-el↗

arXiv2016

The emergence of giant multicaloric phenomena near room temperature

Caloric responses (temperature changes) can be induced in solid-state materials by applying external stimuli such as stress, pressure, and electric and magnetic fields. The magnetic-field-stimulated response is called the magnetocaloric effect, and materials that exhibit this property have long been sought for applications in room temperature magnetic cooling due to their potentially superior efficiency and low impact on the environment. Other solid-state caloric phenomena are less developed, but are likewise under intense investigation. Here we introduce a new material that not only displays giant barocaloric (hydrostatic-pressure-induced) properties, but also a large magnetocaloric response near room temperature. It is unprecedented that two caloric effects of such extreme magnitude occur in the same material and at the same temperature. These effects originate from a magnetostructural transition and a magneto-volume (magnetostriction) effect where the volume change is large enough to force the system from a localized ordered state into an itinerant paramagnetic state.

cond-mat.mtrl-sci↗

arXiv2015

Effects of pressure on the magnetostructural and magnetocaloric properties of isostructurally alloyed (MnNiSi)1-x(FeCoGe)x

The isostructural alloying of two compounds with extremely different magnetic and thermo-structural properties has resulted in a new system, (MnNiSi)1-x(FeCoGe)x, that exhibits extraordinary magnetocaloric properties with an acute sensitivity to applied hydrostatic pressure (P). Application of hydrostatic pressure shifts the first-order phase transition to lower temperature ($Δ$ T=-41 K with P=3.43 kbar) but preserves the giant value of isothermal entropy change (-$Δ$S$\max$=143.7 J/kg K for a field change of ΔB=5 T at atmospheric pressure). Together with the magnetic field, this pressure-induced temperature shift can be used to significantly increase the effective relative cooling power.

cond-mat.mtrl-sci↗

arXiv2014

Pressure-induced giant enhancement of magnetocaloric effects in MnNiSi-based systems

A remarkable decrease of the structural transition temperature of MnNiSi from 1200 K to <300 K by chemically alloying it with MnFeGe results in a coupling of the magnetic and structural transitions, leading to a large magnetocaloric effect near room temperature. It was found that the magnetostructural transition is highly sensitive to external (hydrostatic) pressure: relatively low hydrostatic pressures (~2.4 kbar) lead to an extraordinary enhancement of the isothermal entropy change from $-$Δ$S$ = 44 to 89 J/kg K at ambient (atmospheric) and 2.4 kbar applied pressures, respectively, for a field change of Δ$H$ = 5 T. This giant entropy change is associated with a large relative volume change of about 7% induced by 2.4 kbar applied pressure during the magnetostructural transition. The pressure-enhanced magnetocaloric effects are accompanied by a shift in transition temperature, an effect that may be exploited to tune the transition to the required working temperature, and thereby eliminate the need for a given material to possess a large magnetocaloric effect (i.e., entropy change) over a wide temperature range. Furthermore, this material also possesses negligible hysteresis losses.

cond-mat.mtrl-sci↗

arXiv2010

Physical properties of the non-centrosymmetric superconductor Nb0.18Re0.82

We report the synthesis and measurements of magnetic, transport, and thermal properties of polycrystalline Nb0.18Re0.82, which has a superconducting transition at Tc ~ 8.8 K. The non-centrosymmetric alpha-Mn structure of the compound is confirmed by X-ray diffraction. Using the measured values for the lower critical field Hc1, upper critical field Hc2, and the specific heat C, we estimate the thermodynamic critical field Hc(0), coherence length ξ(0), penetration depth λ(0), and the Ginzburg-Landau parameter κ(0). The specific heat jump at Tc, ΔC/γTc = 1.86, suggests that Nb0.18Re0.82 is moderately coupled superconductor. Below Tc the electronic specific heat decays exponentially, suggesting that the gap is isotropic. Our data suggests that the triplet admixture is weak in the polycrystalline form of compound. However, the estimated value of the upper critical field Hc2(0) is close to the calculated Pauli limit indicating the need for single crystal measurements.

cond-mat.supr-con↗