Experimental first order reversal curves (FORC) on Ising and Heisenberg spin glasses

The first order reversal curve (FORC) method is employed to analyse the low temperature hysteresis behaviour of two model 3d spin glasses: the Ising system Fe0.5Mn0.5TiO3 and the near isotropic Heisenberg like system Ag(11 at % Mn). The hysteresis loops of the two samples are strikingly different (in accord with results from earlier investigations on spin glasses with different anisotropy). The derived FORC distribution of the Ising system is wide, centred around 0-bias field and in parts similar to what has been observed for interacting magnetic nanoparticle systems with wide particle size distributions. The FORC distribution for the Ag(Mn) spin glass on the other hand shows a sharp peak at a weak negative bias field and a coercive field of about - 80 and 200 Oe, respectively. (c) 2006 Elsevier B.V. All rights reserved.