Thickness-Dependent Curie Temperatures of Ultrathin Magnetic Films: Effect of Range of Spin-Spin Interactions
Abstract
A recent paper by Henkel et al.[1] argued that the apparent discrepancy between an effective shift exponent λ=3.0, obtained from a power law fit to experimental data on ultrathin ferromagnetic films, and the finite size scaling prediction λ=1/nu, (nu=2/3 for a Heisenberg ferromagnet), arises from correction terms dependent on the value of phenomenological spin-spin coupling. We present a simple model of spin-spin coupling which provides insight into the nature of the rapid decrease in the Curie temperature with decreasing thin film thickness n ( number of monolayers)[2]. The shift of Curie temperature t(n) = 1-Tc(n)/Tc(bulk) follows the usual power law t(n) n^(-λ) in thick films crossing over to linear behavior t(n) n in the ultrathin film thickness limit. Experimental results for ferromagnetic Ni, Co and Gd thin films and antiferromagnetic CoO films prove the model. [1] M. Henkel, S. Andrieu, P. Bauer, and M. Piecuch, Phys. Rev. Lett. 80, 4783 (1998). [2] R. Zhang, and R. F. Willis, Phys. Rev. Lett.(submitted).
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2001
- Bibcode:
- 2001APS..MARG22012Z