Magnetic Ordering in Polycrystalline NixZn1?xO Solid Solutions

Abstract

In order to examine the influence of the dilution of magnetic ions on the crystal and magnetic structure of NixZn1—xO (x = 1, 0.90, 0.80, 0.70) solid solutions we have performed neutron diffraction experiments on each sample at seven temperatures between 10 and 295 K. To determine the Néel temperatures, the magnetic susceptibility measurements were done in the temperature region between room temperature and 600 K. Starting from the known rhombohedral distortion the crystal structure has been refined in the trigonal space group R3¯m. In this space group the cations occupy octahedral 3a position (with the local symmetry 3¯m), while the oxygen anion is placed in the 3b position (with the local symmetry 3¯m). The magnetic structure for all concentrations x is found to be antiferromagnetic and the magnetic cell is the doubled nuclear cell along the c-axis. The magnetic atoms are arranged in the planes (003) in respect to the nuclear cell. The magnetic moments of two Ni2+ ions in adjacent sheets are oriented antiparallely and the magnetic vector makes an angle of 66° with the c-axis. The magnetic structure is preserved upon random site dilution of the magnetic ions. This is additionally confirmed from the Brillouin-type dependence of the magnetization on temperature as well as from the t = TN(x)/TN(1) versus x variation obtained from the magnetic susceptibility measurements. Concentration dependence of the Néel temperature also shows that NixZn1—xO behaves like a Heisenberg antiferromagnet with the dominant nearest-neighbor interaction, in agreement with the similar (Ni, Co)xMg1—xO solid solution.