Magnetotransport properties of hard magnetic pinned multilayers

Abstract

Hard magnetic (HM) thin films have been vertically integrated below giant magnetoresistive (GMR) multilayer sensors in order to shift the operating point of an applicable GMR sensor. The shift in maximum magnetoresistance (MR) peaks was found to be dependent on the thickness of the HM layer. As a result of different bias geometries, which have been tested, current shunting effects mainly reduce the maximum MR amplitudes. A strong microstructural influence on the magnetotransport has been found; meander-shaped microstructures with different stripe widths have been microfabricated in order to investigate the influence of shape anisotropy and stray field geometry on the magnetotransport. As a result, the bias strength, as well as the shape of the HM hysteresis, varies with the underlying microstructured pattern geometries and the angle of applied field. Comparing the major MR loops of meanders with 1.5, 5, and 10 μm structure width of HM/GMR systems, different MR behavior has been found. It was determined that the MR loops are shifted by different field values simultaneously with a change in the MR loop shape. The effect depends on the orientation of applied field with respect to the meander structure, as well as on the structure width. A creeping effect, which demagnetizes the hard layer, has not been observed during sine-shaped switching cycles. The MR response signal of biased multilayers can be understood using numerical calculations.

Giant Magnetoresistance: Basic Concepts, Microstructure, Magnetic Interactions and Applications

“…To obtain a high anisotropy and therefore a strong alignment, a high aspect ratio of the GMR structure has to be achieved. For example, for realization of linear transition regions in the range of several mT, the width of the GMR device has to be structured down to sizes of 1 µm and below [ 41 , 42 ]. A configuration which considers these aspects is the arrangement of meander shaped GMR sensors in a Wheatstone bridge [ 43 ].…”