论文标题
磁体和自旋转变贡献铁磁性CR掺杂MNTE的热容量：顺磁性自旋效应效应的实验证据
Magnon and Spin Transition Contribution in Heat Capacity of Ferromagnetic Cr-doped MnTe: Experimental Evidence for a Paramagnetic Spin-Caloritronic Effect
论文作者
论文摘要
我们提供了实验证据，证明了对铁磁（FM）CR掺杂MNTE（TC〜280K）中热容量的同时存在和自旋状态过渡的贡献，其中镁热容量归因于观察到的镁双极载体载流子吸热器。原始的抗铁磁（AFM）MNTE仅在Neel温度附近的热容量（Tn〜307K）附近显示镁诱导的峰。然而，掺杂CR的MNTE显示了〜293K处的镁成分峰值峰，在780K附近的深磁性域中附加了峰。温度依赖性的磁化率表明，由于Cr离子诱导的较高的晶体场，CR掺杂最初会在附近和低于TN的MNTE中产生低自旋（LS）状态MN2+离子。在400K以上，LS MN2+离子开始转换为高旋转（HS）MN2+离子。 MN2+的LS-TO-HS过渡会导致过量的熵，从而导致系统中的热量贡献。依赖温度的X射线衍射（XRD）和磁场依赖性敏感性（M-H）分别证实了任何结构变化和磁性偏振子。 XRD和M-H都确保顺磁性结构域中的热容量的峰仅由自旋状态过渡起源。计算热容量与温度，以解释每个组件的贡献，包括由于声子，镁质，自旋变质，Schottky异常和晶格扩张而引起的。随着自旋卡环的最新进展，将基于自旋的效应从磁性材料延伸到磁磁材料中，来自热容量的数据可以发挥至关重要的作用，以探测存在不同现象的存在，例如Paramagnon-Carrier-Drag-Drag和Spin-Roppy Thermophy Thermopowers。
We present experimental evidence for the simultaneous existence of the magnons and spin-state transition contributions to the heat capacity in ferromagnetic (FM) Cr-doped MnTe (Tc~280K), where the magnon heat capacity is attributed to the observed magnon-bipolar carrier-drag thermopower. The pristine antiferromagnetic (AFM) MnTe shows only a magnon-induced peak in the heat capacity near the Neel temperature, TN~307K. However, Cr-doped MnTe shows a magnon-contributed heat capacity peak at ~293K with an additional peak in the deep paramagnetic domain near 780K. Temperature-dependent magnetic susceptibility reveals that Cr-doping initially creates low-spin (LS) states Mn2+ ions into MnTe near and below TN due to a higher crystal field induced by Cr ions. Above 400K, LS Mn2+ ions start converting into high-spin (HS) Mn2+ ions. The LS-to-HS transition of Mn2+ leads to an excess entropy and hence excess heat capacity contribution in the system. Temperature-dependent X-ray diffraction (XRD) and magnetic field-dependent susceptibility (M-H) confirmed no presence of any structural changes and magnetic polaron, respectively. Both XRD and M-H ensure that the peak of the heat capacity in the paramagnetic domain is originated solely by the spin-state transition. The heat capacity versus temperature was calculated to explain the contribution of each component, including the ones due to the phonons, magnons, spin-transition, Schottky anomaly, and lattice dilation. With the recent advances in spin-caloritronics extending the spin-based effects from magnetic to paramagnetic materials, the data from the heat capacity can play a crucial role to probe the presence of different phenomena such as paramagnon-carrier-drag and spin-entropy thermopowers.
