Galvanomagnetic effects in amorphous film alloys

Abstract

Measurements of the spontaneous Hall effect and magnetization of a series of rare earth-transition metal amorphous film alloys fit a model that the Hall asymmetric scattering is simply the sum of the Hall angles of the alloy components. Alloys of the form Gd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.2</inf> (TM) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.8</inf> where TM is Mn, Fe, Co or Ni show a maximum of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\rho_{H}/\rho</tex> the Hall angle, (where ρ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</inf> is the Hall resistivity and ρ the sample resistivity) for Gd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.2</inf> (TM) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.8</inf> of 6%. We find that other rare earth elements have lower <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\rho_{H}/\rho</tex> ratios than Gd and that Nd-Fe alloys exhibit a smaller <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\rho_{H}/\rho</tex> than Gd-Fe because the Nd moments are in an disordered state. Of the alloys studied Gd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.2</inf> (TM) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.8</inf> is suitable for a Hall sensor because R <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> the spontaneous Hall coefficient ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\rho_{H} = R_{s}4\piM</tex> ) is also large, approximately 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> μΩcm/G. This is because Gd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.2</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.8</inf> is a nearly compensated ferrimagnet and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4\piM</tex> is low. The anisotropic magnetoresistance in rare earth-transition metal alloys is about 0.1 to 0.2% and does not scale with ρ. The Corbino disc type magnetoresistance is found to be smaller than expected because in the demagnetized state magnetic domains remain effective Hall scatterers.