Spin canting and magnetic relaxation phenomena in Mn 0.25Zn 0.75Fe 2O 4

Abstract

The magnetic properties of the ferrite Mn 0.25Zn 0.75Fe 2O 4 have been studied by Mössbauer spectroscopy and magnetisation measurements. Mössbauer spectra, obtained at low temperatures and large applied magnetic fields, showed that almost all Fe 3+ ions are in octahedral (B) sites and only about 2% of the Fe 3+ ions are in tetrahedral (A) sites. At 5 K about 16% of the B-site Fe 3+ ions have spins parallel to the A-site magnetisation, but when the temperature is raised to about 40 K, these spins are reversed. Some other B-site Fe 3+ ions show a large spin canting at 5 K and these ions are significantly affected by transverse relaxation at relatively low temperatures. A third group of B-site ions has negligible canting at low temperatures and these ions are only slightly affected by relaxation below 60 K. At low temperatures the material can be described as a cluster spin glass. Above 60 K part of the sample breaks up into superparamagnetic clusters whereas other parts remain ferrimagnetic.