A Monte Carlo analysis of spin dynamics and Mössbauer relaxation in 2-D magnetically diluted iron oxides

Abstract

The spin dynamics of two-dimensional magnetically diluted iron oxides with the K₂NiF₄ structure has been studied by a Monte Carlo analysis using a simple Ising model. Below the critical temperature, antiferromagnetic domains are formed in which the domain walls are ‘pinned’ by the non-magnetic atoms such that increasing dilution causes substantial interpenetration of the domains. The magnetic hysteresis observed in field-cooled and zero-field-cooled magnetic measurements on SrLaFeO₄ diluted with a non-magnetic cation can be explained. Similarly, the observed Mössbauer relaxation can be simulated, and derives from differing relaxation rates for spins with few near neighbour spins, particularly those close to a domain boundary. The existence of ‘spin clusters’ which has often been assumed is not a good model. It is suggested that Ising-like behaviour in the critical region is an important aspect of these diluted Heisenberg layered systems.