MgO barrier-perpendicular magnetic tunnel junctions with CoFe/Pd multilayers and ferromagnetic insertion layers

Abstract

The authors studied an effect of ferromagnetic (Co 20 Fe 60 B 20 or Fe) layer insertion on tunnel magnetoresistance (TMR) properties of MgO-barrier magnetic tunnel junctions (MTJs) with CoFe/Pd multilayer electrodes. TMR ratio in MTJs with CoFeB/MgO/Fe stack reached 67% at annealing temperature (T a ) of 200 o C and then decreased rapidly at T a over 250 o C. The degradation of the TMR ratio may be related to crystallization of CoFe(B) into fcc(111) or bcc(011) texture resulting from diffusion of B into Pd layers. MTJs which were in-situ annealed at 350 o C just after depositing bottom CoFe/Pd multilayer showed TMR ratio of 78% by post annealing at T a =200°C.

Perpendicular magnetic anisotropy and the magnetization process in CoFeB/Pd multilayer films

“…13,15 Thus, in-situ heating during deposition or post annealing is commonly a demand to convert amorphous film into the required crystal structure. 21,22 However, heat treatment of the films with oxide interfaces would easily result in the oxidation and migration (of Boron, Oxygen) that influence on the magnetic properties of the films. [23][24][25] Recently, PMA in multilayer films using amorphous CoFeB layers and noble metal spacing have been reported.…”

Atomic-Layer Alignment Tuning for Giant Perpendicular Magnetocrystalline Anisotropy of3dTransition-Metal Thin Films

“…Pd) elements, [3][4][5][6][7][8][9] which exhibit large PMA that promisingly overcomes the shape in-plane magnetic anisotropy and thermal fluctuations on a device level.…”

Temperature dependent coercivity crossover in pseudo-spin-valve magnetic tunnel junctions with perpendicular anisotropy

“…[10][11][12][13][14] Promising progress has been made not only on reaching high tunneling magnetoresistance (TMR) ratios but also achieving a low critical current density. [15][16][17] Here, we report a temperature dependent effect: coercivity crossover. The TMR of pMTJs with a pseudo spin valve structure disappears in a narrow temperature range, only to reappear at lower temperature.…”