SPIN-POLARIZED MAGNETIC TUNNELING MAGNETORESISTIVE EFFECTS IN VARIOUSJUNCTIONS

Recent progress concerning spin-polarized magnetic tunnelling effects for (i) trilayer standard ferromagnet (F)/insulator (I)/ferromagnet (F ) junctions, (ii) spin-valve-type junctions, (iii) trilayer or multila yer ferromagnet/granular/ferromagnet junctions and (iv) F/I/F junction with a 'wedge-geometry' insulator is reviewed. Special emphasis is pl aced on the dependence of the tunnel magnetoresistance ratio on temper ature and also the intensity of the applied voltage. It was found that the resistiance for the saturation magnetization state, R-S, and the tunnelling magnetoresistance ratio, TMR, of an Fe/Al(2)O3/Fe junction decreased rapidly with increasing temperature, whereas those of a NiFe /Al2O3/Co junction were insensitive to temperature. Concerning the bia s voltage dependence oi Rs and TMR, the same tendency with temperature was observed for Fe/Al2O3/Fe and NiFe/Al2O3/Co junctions. Spin-valve- type junction exchange biased by a FeMn layer exhibits a relatively la rge TMR ratio up to about 400 K.