The correlated random anisotropy model of the Co-organic composite films

V.V. Kabanov,1* A.V. Shumilin,1 M. Benini,2 T. Mertelj,1 V.A. Dediu2

1Jozef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia

2CNR-ISMN, Via Piero Gobetti 101, 40129, Bologna, Italy

*viktor.kabanov@ijs.si

We propose the correlated random anisotropy model that describes thin ferromagnetic films hybridized with organic molecular layers. The asymmetry of the molecules leads to the random in-plane anisotropy induced at the surface of the magnetic film. We show that this strongly modifies the magnetic anisotropy of the whole cobalt layer which magnitude critically depends on the correlation radius of random anisotropy (fig. a). When this radius is small even strong induced anisotropy can be neglected. However, with the increase of correlation radius, the effect of molecules starts to dominate the magnetic properties. It results in the colossal increase of the coercive field, modification of the hysteresis loop shape (fig. b), and breaking of the Raleigh law at low fields.

Physically, the effect results from the modification of pseudoground states in the magnetic film. At a low correlation radius the state can be described by standard domain wall picture, while at larger correlation radiuses a correlated spin glass state emerges.

Acknowledgements

We acknowledge the support of the EC projects INTERFAST (H2020-FET-OPEN-965046).

Fig. 1. a) The correlation radius rc of molecule-induced anisotropy. b) Hysteresis loops for different values of rc.