Influence of Temperature and Annealing on GMR in Sputtered Permalloy/Cu Multilayers

M. Urbaniaka, F. Stobieckia, T. Lucińskia, M. Kopcewiczb, A. Grabiasb and J. Aleksiejewa a Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland b Institute of Electronic Materials Technology, Wólczyńska 133, 01-919 Warszawa, Poland

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The influence of temperature and annealing on giant magnetoresistance of Si(100)/Cu(20 nm)/Py(2 nm)/(Cu(2 nm)/Py(2 nm))100 multilayer (Py = Ni83Fe17) sputtered at room temperature in double face-to-face configuration is reported. It was found that giant magnetoresistance value, ΔRGMR/Rsat (where Rsat is the resistance in saturation), monotonically decreases with increasing temperature (4.5% at 173 K to about 1% at 373 K). This results from the decrease in magnetic change of resistance, ΔRGMR, and to the lesser extent from an increase in Rsat, though both of them are caused by the shortening of electrons mean free path. The observed almost linear decrease in giant magnetoresistance saturation field with increasing temperature is explained by temperature changes of magnetization profile. Vibrating sample magnetometer measurements revealed that the increase in temperature results in pronounced decrease in remnant to saturation magnetization ratio (Mr/Ms) suggesting that at low temperatures magnetic bridges between Py layers play an important role in magnetization process. It is shown that proper annealing, by an annihilation of bridges and/or lateral decoupling, leads to an increase in giant magnetoresistance ratio from 3.4% in as deposited state to 4.7%.

DOI: 10.12693/APhysPolA.97.539 PACS numbers: 75.70.Ak, 75.70.Pa