Magnetoresistance of microscopic strips of thin (NiFe/Ag) multilayers with large bi-quadratic coupling

Abstract

The magnetoresistance of microscopic strips of (NiFe/Ag) multilayers with large bi-quadratic coupling has been measured. When the field is applied along the length of the strip, the magnetoresistance has an almost linear R(H) characteristic. On the other hand, when the field is applied transversely i.e. in the plane of the film but perpendicular to its length, a plateau in the resistivity is observed up to a critical field, Hcrit, which depends on the shape anisotropy of the strip. Above this field, R(H) decreases as in the longitudinal case. Computer simulations have been undertaken to explain this behaviour. The plateau observed with a transverse applied field is due to the effect of the shape anisotropy on the remanent magnetization of the multilayers. This remanent magnetization can be quite large because of the significant bi-quadratic coupling between the layers.