Sign reversal in the exchange bias and the collapse of hysteresis width across the magnetic compensation temperature in a single crystal of Nd0.75Ho0.25Al2
Sign reversal in the exchange bias and the collapse of hysteresis width across the magnetic compensation temperature in a single crystal of Nd0.75Ho0.25Al2
复制标题
DOI：
10.1209/0295-5075/86/47003
复制
发表时间：
2008-12
期刊：
影响因子：
--
通讯作者：
P. D. Kulkarni;A. Thamizhavel;V. C. Rakhecha;A. Nigam;P. Paulose;S. Ramakrishnan;A. Grover
中科院分区：
文献类型：
--
作者：
P. D. Kulkarni;A. Thamizhavel;V. C. Rakhecha;A. Nigam;P. Paulose;S. Ramakrishnan;A. Grover
在混合Nd 0.75Ho0.2 5Al 2系统中，占据同一晶位的Nd和Ho的磁矩是反铁磁耦合的，所选择的化学计量比在所有取向上都表现出磁补偿行为（Tcomp = 2 4K）.在T comp附近，传导电子极化（CEP）承担耦合到包括Nd/Ho矩的伪反铁磁体的软铁磁体交换的作用，导致滞后（M-H）回路中的不对称性，即，交换偏置场（exchange bias field，H exch）在T comp上，CEP贡献反转符号，并且在协调中，M-H环路中的不对称性也经历相位反转。有趣的是，M-H环的宽度显示出发散，然后从两端接近Tcomp时出现崩溃。所观察到的行为证实了一个长期的预测的基础上的亚铁磁系统的唯象模型。跨T_comp的场致变化在热容数据中留下准相变的印记。磁电阻（Δ R / R vs T）具有振荡响应，其中可以识别跨Tc和Tcomp的变化。
In the admixed Nd 0.75 Ho 0.25 Al 2 system, magnetic moments of Nd and Ho occupying the same crystallographic site are antiferromagnetically coupled and the chosen stoichiometry displays a magnetic compensation behavior ( T comp ≈ 24 K) in all orientations. In the vicinity of T comp , the conduction electron polarization (CEP) assumes the role of a soft ferromagnet exchange coupled to a pseudo-antiferromagnet comprising Nd/Ho moments, resulting in an asymmetry in the hysteretic ( M - H ) loop, i.e., the notion of an exchange bias field ( H exch ). Across T comp , the CEP contribution reverses sign, and in consonance, the asymmetry in the M - H loop also undergoes a phase reversal. Interestingly, the width of the M - H loop shows a divergence, followed by a collapse on approaching T comp from either end. The observed behavior confirms a long standing prediction based on a phenomenological model for ferrimagnetic systems. The field induced changes across T comp leave an imprint of a quasi -phase transition in the heat capacity data. Magneto-resistance ( ∆ R / R vs T ) has an oscillatory response, in which the changes across T c and T comp can be recognized.