Peculiarities of field dependence of low-temperature magnetization and transparency effect in a magnet with biaxial anisotropy

A spin model of a paramagnetic ion for which anisotropy in the easy plane is describe by a certain type of spin multipoles is considered. It is shown that in spite of the absence of axial symmetry in such a model, there are intervals of values of longitudinal (normal to the easy plane) magnetic field in which the magnetization component along a chosen axis in the ground state has a definite value. In particular, it is possible to attain the nominal value of magnetization in a finite field. Besides, the excitation by a longitudinal varying magnetic field permits the observation of ‘‘transparency”, i.e., the disappearance and subsequent reappearance of varying field absorption, upon a change in a constant field. The manifestation of biaxial anisotropy in a Heisenberg magnet is investigated. It is shown that the behavior of a magnetically ordered system under certain conditions resembles the behavior of an individual magnetic ion. The difference is exhibited, for example, in the response to a varying field.

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