Al-doping effect on the structural and physical properties of delafossite-type oxide CuCrO_2

摘要

The structure, Raman spectroscopy, magnetization, and dielectric properties of delafossite-type oxide CuCr_(1-x)Al_xO_2 have been characterized. It was found that Al substitution generates an anisotropic effect on the structure, besides magnetic dilution. The temperature dependence of all samples exhibits paramagnetic behavior at high temperature. Above x=0.2 the ferromagnetic transition at 120 K disappears. It is argued that Al substitution destabilizes the antiferromagnetic order of Cr~3 ions and modulates the spin configuration, leading to a weak ferromagnetism. The coupling between the magnetic order and ferroelectric order is also characterized.