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Characterisation of Permalloy based thin films and magnetic multilayers using the magnetoresistance and Hall effect measurements
|Marius Volmer 1, Jenica Neamtu 2|
1. Transilvania University, Physics Department, Eroilor 29, Brasov 2200, Romania
Correlation between the Hall effect and magnetization enables the use of this technique for the study of magnetic properties in Permalloy (Py) thin films and Py/NM/Py multilayers. NM denotes Cu, Mo and Al2O3 layers. We made the measurements at room temperature in a setup which allows us to perform both Hall effect and magnetoresistance measurements. The Hall effect measurements were performed for different values of the angle between the magnetic field and the normal to the film plane from 0 to 90 degrees. The measured voltages present hysteresis loops at low magnetic field. Because at low magnetic fields the shape anisotropy forces the magnetization to rotate in the film plane what we have is a Planar Hall Effect (PHE) signal which can be used as probe of magnetization reversal. Basically, PHE is an Anisotropic Magnetoresistance Effect (AMR). The PHE measurements were employed to evaluate the magnetization reversal process and the coupling between the magnetic layers. We explain the hysteretic behaviour of the Hall voltage using a simple phenomenological model in which the extraordinary Hall coefficient is expressed as the sum of two terms: a field-independent extraordinary Hall coefficient and a coefficient corresponding to the magnetically disordered state which is related to the AMR and GMR effects. We made also measurements of the Hall voltage as a function of the applied field orientation θ (from 0 to 360 degrees) in order to estimate the perpendicular anisotropy. We complete this discussion using a micromagnetic simulator which can show us the spin distribution for different values of the applied magnetic field and can calculate the hysteresis loop of the sample. The results are related with the samples microstructure. The saturation fields obtained when the magnetic field is applied normal to the film plane are less than the values predicted from the shape anisotropy known for flat surfaces, but are consistent with the film surfaces topography.
Presentation: poster at E-MRS Fall Meeting 2003, Symposium B, by Marius Volmer
See On-line Journal of E-MRS Fall Meeting 2003
Submitted: 2003-05-27 12:13 Revised: 2009-06-08 12:55