We report the observation of large magnetocaloric effect near room temperature in antipervoskite SnCMn3. The maximal magnetic entropy change at the first-order ferrimagnetic-paramagnetic transition temperature (TC 279 K) is about 80.69mJ/cm3 K and 133mJ/cm3 K under the magnetic field of 20 kOe and 48 kOe, respectively. These values are close to those of typical magnetocaloric materials. The large magnetocaloric effect is associated with the sharp change of lattice, resistivity and magnetization in the vicinity of TC. Through the measurements of Seebeck coefficient and normal Hall effect, the title system is found to undergo a reconstruction of electronic structure at TC. Considering its low-cost and innocuous raw materials, Mn-based antiperovskite compounds are suggested to be appropriate for pursuing new materials with larger magnetocaloric effect.
The magnetic and magnetocaloric properties of polycrystalline La0.70(Ca0.30-xSrx)MnO3:Ag 10% manganite have been investigated. All the compositions are crystallized in single phase orthorhombic Pbnm space group. Both, the Insulator-Metal transition temperature (TIM) and Curie temperature (Tc) are observed at 298 K for x = 0.10 composition. Though both TIM and Tc are nearly unchanged with Ag addition, the MR is slightly improved. The MR at 300 K is found to be as large as 31% with magnetic field change of 1Tesla, whereas it reaches up to 49% at magnetic field of 3Tesla for La0.70Ca0.20Sr0.10MnO…
Magneto-resistive and magneto-caloric properties of polycrystalline Pr2/3Sr1/3MnO3 have been studied as a function of sintering temperature (Ts) between 1260-1450°C. Reitveld refinement of their X-ray diffraction (XRD) patterns confirms their single phase crystalline structure with orthorhombic Pbnm space group. The point of maximum value of temperature coefficient of resistance (TCRmax) and Curie temperature (Tc) decreased slightly with Ts. Magneto-resistance (MR) and magnetic entropy (ΔSM) increased markedly with sintering temperature. This could be attributed to the observed sharpness of bo…
We have investigated magnetization(M), magnetocaloric effect(MCE) and magnetothermopower(MTEP) in polycrystalline Pr0.6Sr0.4MnO3, which shows a second-order paramagnetic to ferromagnetic transition near room temperature (TC = 305 K). However, field-cooled M(T) within the long range ferromagnetic state shows an abrupt decrease at TS = 86 K for H < 3 T. The low temperature transition is first-order in nature as suggested by the hysteresis in M(T) and exothermic/endothermic peaks in differential thermal analysis for cooling and warming cycles. The anomaly at TS is attributed to a structural trans…
We report a comprehensive study on the elastic properties of a hexanary high-entropy alloy superconductor (ScZrNbTa)$_{0.685}$[RhPd]$_{0.315}$ at room and cryogenic temperatures, by Resonant Ultrasound Spectroscopy experiments. The derived elastic constants are bulk modulus $K=132.7$ GPa, Young's modulus $E=121.0$ GPa, shear modulus $G=44.9$ GPa, and Poisson's ratio $ν$=0.348 for room temperature. The Young's and shear moduli are $\sim 10\%$ larger than those in NbTi superconductor with similar $T_c$, while the ductility is comparable. Moreover, the mechanical performance is further enhanced a…
The magnetic and magnetocaloric properties of Ga1-xCMn3+x have been investigated. Reversible magnetocaloric effect (MCE) occurs near the Curie temperature TC. The magnetic entropy change decreases with increasing x, though TC and magnetization increases. Meanwhile, the temperature span of vs. T plot becomes well broadened with x. Due to the competition between the broadening temperature span and decreasing, the relative cooling power (RCP) increases initially, and then decreases with increasing x. The largest RCP (2.1 J/cm3, under 45 kOe) observed when x=0.07 (TC = 296.5 K) is comparable to th…
We investigate the magnetocaloric effect (MCE), relative cooling power (RCP) and crystalline structure in Sb substituted CrTe_{1-x}Sb_{x} (0 \leq x \leq 0.2) alloy. The Rietveld refinement of the XRD pattern of CrTe1-xSbx showed the emerging of pure hexagonal NiAs structure with P63/mmc (194) space group with increasing Sb substitution. We detect a slight increase in the basal plane a-lattice parameter, with a much larger reduction in the c-axis. Magnetic isotherms were measured in the temperature range of 50-400K. The results revealed an increase in the maximum entropy change |S_{M}(T,H)| wit…
The effect of Co on the structural, magnetic and magnetocaloric effect (MCE) of Ni50-xCoxMn38Sb12 (x=0,2,3,4,5) Heusler alloys was studied. Using x-ray diffraction, we show the evolution of the martensitic phase from the austenite phase. The martensitic transition temperature is found to decrease monotonically with Co concentration. Remarkable enhancement of MCE is observed near room temperature upon Co substitution. The maximum magnetic entropy change of 34 Jkg-1K-1 was achieved in x=5 at 262 K in a field of 50 kOe and a value of 29 Jkg-1K-1 found near room temperature. The significant increa…
We studied the magnetic properties of bulk LaCrO3; a GdFeO3-type distorted perovskite, with a predominant antiferromagnetic phase transition at ~ 290 K. The bulk LaCrO3 exhibits intrinsic weak ferromagnetism at room temperature, which may arise due to the tilting of CrO6 octahedra, resulting in a non-zero net magnetic moment, as confirmed from the magnetization measurements. A broad magnetically-induced entropy change (-ΔS) is observed with the maximum at 290 K, close to room temperature in LaCrO3 system.
The gigantic decrease of resistance by an applied magnetic field, which is often referred to as colossal magnetoresistance (CMR), has been an attracting phenomenon in strongly correlated electron systems. The discovery of CMR in manganese oxide compounds has developed the science of strong coupling among charge, orbital, and spin degrees of freedom. CMR is also attracting scientists from the viewpoint of possible applications to sensors, memories, and so on. However, no application using CMR effect has been achieved so far, partly because the CMR materials which satisfy all of the required con…
We calculate the in-plane Seebeck coefficient of Sr$_2$RuO$_4$ within a framework combining electronic structure and dynamical mean-field theory. We show that its temperature-dependence is consistent with entropic considerations embodied in the Kelvin formula, and that it provides a meaningful probe of the crossover out of the Fermi liquid regime into an incoherent metal. This crossover proceeds in two stages: the entropy of spin degrees of freedom is released around room-temperature while orbital degrees of freedom remain quenched up to much higher temperatures. This is confirmed by a direct …
Polycrystalline CrTe1-xSex samples were prepared using the conventional solid-state reaction technique and characterized by x-rad diffraction, temperature- and field- dependent magnetization for possible use in magnetocaloric cooling. Rietveld refinement revealed two phases in all prepared samples; a minor monoclinic phase that decreases with Se concentration until it vanishes near 10% of Se, and a major hexagonal one. At high temperature, CrTe1-xSex is paramagnetic, with ferromagnetic phase transition occurs at Tc ~332, 320, 318, 310, 299, and 295 K for x= 0.00, 0.02, 0.04, 0.06, 0.08, and 0.…
In many transition-metal oxides and dichalcogenides, the electronic and lattice degrees of freedom are strongly coupled, giving rise to remarkable phenomena, such as metal-insulator transition (MIT) and charge-density wave (CDW) order. We study this interplay by tracing the instant electronic structure under ab initio molecular dynamics. Applying this method to a 1T-TaS2 layer, we show that the CDW-triggered Mott gap undergoes a continuous reduction as the lattice temperature raises, despite a nearly constant CDW amplitude. Before the CDW order undergoes a sharp first-order transition around t…
Scaling behavior in thermoelectric misfit cobalt oxides
我们研究了失配钴氧化物[Bi $_{1.7}$ Co $_{0.3}$ Ca $_{2}$ O $_{4}$ ] $^{RS}_{0.6}$ CoO $_{2}$的热电和热力学性质。发现一个大的负磁热电势的规模与磁场和温度揭示了显着的自旋熵贡献的热电性能产生一个常数S $_0\approx$ 60 $μ$ V K $^{-1}$等于高温渐近值的自旋1/2熵。低温比热测量使我们能够确定增强的电子部分与$γ\approx$ 50 mJ（摩尔K $^{2}$）$^{-1}$证明强相关性。因此，[Bi $_{1.7}$ Co $_{0.3}$ Ca $_{2}$ O $_{4}$ ] $^{RS}_{0.6}$ CoO $_{2}$、其他钴矿以及其他材料之间的关键比较揭示了作为$γ$的函数的热电低温斜率的普遍行为，从而证明了纯电子起源。这种潜在的通用标度行为表明，在失配钴氧化物的热电势的高室温值的结果从增加的自旋熵的贡献，以扩大电子之一。
The effect of pressure on the magnetic and the magnetocaloric properties around the martensitic transformation temperature in NiCoMnSb Heusler alloy has been studied. The martensitic transition temperature has significantly shifted to higher temperatures with pressure, whereas the trend is opposite with the application of applied magnetic field. The maximum magnetic entropy change around the martensitic transition temperature for Ni45Co5Mn38Sb12 is 41.4 J/kg K at the ambient pressure, whereas it is 33 J/kg K at 8.5 kbar. We find that by adjusting the Co concentration and applying suitable pres…
