Low dimensional double molybdates and tungstates – strongly anisotropic magnetic materials

Eugene N. Khatsko 

Institute for Low Temperature Physics, 47 Lenin ave., Kharkov 61103, Ukraine

Abstract

Magnetic properties of double rare earth molybdates and tungstates (general formulae - MR(XO4)2, where M = Cs, K, Rb, R = rare earth, and X = Mo, W) are of interest because these crystals display a number of fascinating peculiar its features associated with a low symmetry of the crystal lattice, a relatively small value of exchange, a considerable contribution of the dipole-dipole interaction of magnetic ions, the low dimensionality of a magnetic structure, and the competition between magnetic and electric interaction, which determines the energy spectrum of the magnetic ions and its features.

The layered structure and strong electron-phonon interaction, together with a degenerate or quasidegenerate electronic ground state, make these compounds structurally unstable; they typically exhibit several structural phase transition induced by weak external fields (temperature or magnetic).

It should be mentioned promising use these materials in engineering.

The magnetic susceptibility, the magnetization, and resonant investigations of this class of compounds are reported. The measurements were performed at temperatures between 0,5 and 100 K in magnetic fields up to 7 T along three principal magnetic axes. The magnetic properties are strongly anisotropic in all investigated temperature region, that is dictated by crystal structure and intricate character of magnetic interactions. The EPR investigation carried in wide range of frequencies (10-190 GHz) at 1.8-30 K allow to establish detailed characteristic and quantity of nonequivalent magnetic centers, including g-factors parameters and structure of magnetic ions energy spectrum.

Magnetic susceptibility measurements indicate diverse quantity and type of exchange interaction in different directions.

On the base of experimental data the magnetic structures of compounds are proposed. They demonstrate variety of structures – from simple collinear to noncollinear many sublatices ones.

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Presentation: oral at E-MRS Fall Meeting 2005, Symposium B, by Eugene N. Khatsko
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-30 15:29
Revised:   2009-06-07 00:44
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