Coupled order parameters, lattice disorder, and magnetic phase transitions
Coupled order parameters, lattice disorder, and magnetic phase transitions
复制标题
DOI：
10.1103/physrevb.12.2741
复制
发表时间：
1975-10
影响因子：
3.7
通讯作者：
B. Huberman;W. Streifer
中科院分区：
文献类型：
--
作者：
B. Huberman;W. Streifer
发展了平均场理论来描述晶格无序对磁相变的影响。根据参数值的不同，T C 可能会出现三种类型的重整化效应，即弱、强或灾难性的。最后一个意味着磁和晶格参数中的一阶相变。获得的相图显示了临界三相点的存在以及声子熵在确定 T C 中的影响。还表明，即使在弱耦合极限下，晶格无序过程也可以仅由磁熵驱动。该模型适用于 MnBi，它会经历远低于其平均场值居里温度的一阶磁相变。
A mean-field theory is developed which describes the effects of lattice disorder on magnetic phase transitions. Depending on the parameter values, three types of renormalization effects on T C can occur, ie, weak, strong, or catastrophic; the last implies a first-order phase transition in both magnetic and lattice order parameter. Phase diagrams are obtained which show both the existence of critical triple points and the effects of phonon entropy in determining T C. It is also shown that even in the weak-coupling limit, the lattice disordering process can be driven by magnetic entropy alone. The model is applied to MnBi, which undergoes a first-order magnetic phase transition well below its mean-field-value Curie temperature.