ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
A recently developed method1 for the magnetoresistive measurement of the exchange constant in Permalloy films is applied to multiple films of varied thickness. Passing a dc current along the easy axis of a thin-film single-domain Permalloy stripe generates an inhomogeneous internal magnetic field. This field opposes exchange forces and causes the film magnetization to fan in opposite directions through the film thickness, forming a variable angle Bloch wall parallel to, and extending throughout, the film plane. The magnetization fanning is readily observable via dc magnetoresistive detection. Values for the exchange constant A are obtained by comparing experimental measurements with a micromagnetic model1 that employs A as the single free parameter. Present measurements on several films of thickness between 2000 and 4000 A(ring) confirm the predicted strong film thickness dependence of magnetization fanning amplitude, and are all shown to be consistent with a single value for the Permalloy exchange constant of A=1.1±0.1×10−6 ergs/cm. This value is equal to the previous1 independently obtained value. The present technique for measurement of A is demonstrated to yield consistent values for the exchange constant in different films of varied thickness, and does not require additional postulates (as do spin-wave resonance techniques) concerning surface anisotropy or saturation magnetization inhomogeneities.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.340912
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