Fabrication and characterization of thin films with perpendicular magnetic anisotropy for high-density magnetic recording

Chen, C. W.

doi:10.1007/bf01124655

Cited by 10 publications

(1 citation statement)

References 132 publications

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“…This work was followed by experiments carried out on ultrathin NiFe films grown on Cu(111) [2] which confirmed the interfacial nature of the perpendicular magnetic anisotropy (PMA) observed in this system. Within the last fifty years a lot of work has been carried out on interfacial anisotropy both from theoretical and experimental points of view [3][4][5][6][7][8]. Nowadays, perpendicular interfacial anisotropy has become one of the main ingredients of novel magnetic memory elements employing out-of-plane magnetized (perpendicular) magnetic tunnel junctions (pMTJ) stacks [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Second order anisotropy contribution in perpendicular magnetic tunnel junctions

Timopheev¹,

Sousa²,

Chshiev³

et al. 2016

Sci Rep

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Hard-axis magnetoresistance loops were measured on perpendicular magnetic tunnel junction pillars of diameter ranging from 50 to 150 nm. By fitting these loops to an analytical model, the effective anisotropy fields in both free and reference layers were derived and their variations in temperature range between 340 K and 5 K were determined. It is found that a second-order anisotropy term of the form −K2cos4θ must be added to the conventional uniaxial –K1cos2θ term to explain the experimental data. This higher order contribution exists both in the free and reference layers. At T = 300 K, the estimated −K2/K1 ratios are 0.1 and 0.24 for the free and reference layers, respectively. The ratio is more than doubled at low temperatures changing the ground state of the reference layer from “easy-axis” to “easy-cone” regime. The easy-cone regime has clear signatures in the shape of the hard-axis magnetoresistance loops. The existence of this higher order anisotropy was also confirmed by ferromagnetic resonance experiments on FeCoB/MgO sheet films. It is of interfacial nature and is believed to be due to spatial fluctuations at the nanoscale of the first order anisotropy parameter at the FeCoB/MgO interface.

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