Computer analysis of Arrott plots of compositionally modulated materials

摘要

We investigated the field and temperature behavior of the magnetization for a simple model of a compositionally‐modulated (CM) material. Our aim is to determine the value of the Curie temperature (TC) for a material which has a large composition modulation. We use Arrott plots to find TC. Our model neglects the exchange interaction between layers and is applied to copper‐nickel CM films. In this model the fraction of nickel along the film can be represented by a sinusoidally varying function. Then, the magnetization at any point along the film normal depends on the nickel fraction at that point. Thus, for any temperature and field, the magnetization can be determined at any position along the film normal. By integrating these magnetizations over a wavelength, we obtain the magnetization of the film for any temperature and field. The Curie temperature obtained from the Arrott plot curves of these data shows that TC of these films arises essentially from TCmax and that only the upper 40% of the compositions contribute to TCmax. Since our model neglects exchange, we did not expect our results to be applicable to films with short‐wavelength modulations. However, TC measured on a 8 Å Cu‐8 Å Ni film agrees closely with the model presented here.