Magnetic properties and structure of the quasi-two-dimensional Ising magnet CsEr(MoO4)2
Abstract
Single crystals of CsEr(MoO4)2 are obtained, their x-ray structural investigations are carried out, and the symmetry group and lattice parameters are determined. The EPR spectral investigations reveal the presence of a paramagnetic Er3+ center with a highly anisotropic, practically Ising-like g-tensor (ga′ = 0.42, gb = 19.2, gc = 1.45). The data of temperature dependences of the magnetic susceptibility of the CsEr(MoO4)2 single crystal reveal a phase transition to the antiferromagnetic state at Tc = 0.84 K. A first-order metamagnetic transition caused by crystallographic anisotropy and competing exchanges is observed in the magnetically ordered state. Above Tc, short-range order effects are observed right up to helium temperatures. Dipole–dipole energy calculations for possible magnetic structures show that the dipole–dipole interaction leads to ferromagnetic ordering in randomly-connected chains at temperatures considerably higher than Tc. It is shown that a three-dimensional collinear magnetic structure of ferromagnetic Ising chains with antiferromagnetic interaction between chains is realized during the magnetic phase transition. The temperature dependences of susceptibility are described quite well in the model of weakly interacting ferromagnetic Ising chains.