Patterned soft magnetic materials are eligible for use in magnetic random access memories. An hexagonal-lattice pattern of circular antidots was produced by optical lithography in a Co film. In order to test the effect of geometry on the local magnetisation configuration of such a structure, we performed room temperature angle-resolved magnetisation measurements aimed to check the pinning of domain walls by the pattern’s lattice. Magnetoresistance (MR) room temperature measurements were performed at various angles between the magnetic field direction and the macroscopic electrical current vector, to clarify if and how the local current density configuration affects the MR response. We found that the magnetoresistance is of anisotropic type (AMR) and has a local origin. Furthermore, the largely unsaturating behaviour of MR at high fields may be explained only by considering that tiny portions of the pattern constitute highly frustrated regions and align their magnetisation at rather high fields. A simplified model based on a local anisotropy term is shown to account for the experimental results for both M and MR.
Magnetoresistance anisotropy in a hexagonal lattice of Co antidots obtained by thermal evaporation
SPIZZO, Federico;
2010
Abstract
Patterned soft magnetic materials are eligible for use in magnetic random access memories. An hexagonal-lattice pattern of circular antidots was produced by optical lithography in a Co film. In order to test the effect of geometry on the local magnetisation configuration of such a structure, we performed room temperature angle-resolved magnetisation measurements aimed to check the pinning of domain walls by the pattern’s lattice. Magnetoresistance (MR) room temperature measurements were performed at various angles between the magnetic field direction and the macroscopic electrical current vector, to clarify if and how the local current density configuration affects the MR response. We found that the magnetoresistance is of anisotropic type (AMR) and has a local origin. Furthermore, the largely unsaturating behaviour of MR at high fields may be explained only by considering that tiny portions of the pattern constitute highly frustrated regions and align their magnetisation at rather high fields. A simplified model based on a local anisotropy term is shown to account for the experimental results for both M and MR.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
