Fieldlike and antidamping spin-orbit torques in as-grown and annealed Ta/CoFeB/MgO layers
Avci, Can Onur (Institut Català de Nanociència i Nanotecnologia)
Garello, Kevin (Institut Català de Nanociència i Nanotecnologia)
Nistor, Corneliu (Institut Català de Nanociència i Nanotecnologia)
Godey, Sylvie. (Institut Català de Nanociència i Nanotecnologia)
Ballesteros, Belén (Institut Català de Nanociència i Nanotecnologia)
Mugarza, Aitor (Institut Català de Nanociència i Nanotecnologia)
Barla, Alessandro (Consiglio Nazionale Delle Ricerche. Istituto di Struttura della Materia)
Valvidares, Manuel (ALBA Laboratori de Llum de Sincrotró)
Pellegrin, Eric. (ALBA Laboratori de Llum de Sincrotró)
Ghosh, Abhijit (ETH Zurich. Department of Materials)
Miron, Ioan Mihai (SPINTEC)
Boulle, Olivier (SPINTEC)
Auffret, Stéphane (SPINTEC)
Gaudin, Gilles (SPINTEC)
Gambardella, Pietro (Institut Català de Nanociència i Nanotecnologia)

Data:	2014
Resum:	We present a comprehensive study of the current-induced spin-orbit torques in perpendicularly magnetized Ta/CoFeB/MgO layers. The samples were annealed in steps up to 300 °C and characterized using x-ray-absorption spectroscopy, transmission electron microscopy, resistivity, and Hall effect measurements. By performing adiabatic harmonic Hall voltage measurements, we show that the transverse (fieldlike) and longitudinal (antidampinglike) spin-orbit torques are composed of constant and magnetization-dependent contributions, both of which vary strongly with annealing. Such variations correlate with changes of the saturation magnetization and magnetic anisotropy and are assigned to chemical and structural modifications of the layers. The relative variation of the constant and anisotropic torque terms as a function of annealing temperature is opposite for the fieldlike and antidamping torques. Measurements of the switching probability using sub-μs current pulses show that the critical current increases with the magnetic anisotropy of the layers, whereas the switching efficiency, measured as the ratio of magnetic anisotropy energy and pulse energy, decreases. The optimal annealing temperature to achieve maximum magnetic anisotropy, saturation magnetization, and switching efficiency is determined to be between 240 and 270°C.
Ajuts:	European Commission 203239 European Commission 318144 Ministerio de Ciencia e Innovación MAT2010-15659
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Publicat a:	Physical review B : Condensed matter and materials physics, Vol. 89, issue 21 (June 2014) , art. 214419, ISSN 1550-235X

DOI: 10.1103/PhysRevB.89.214419

Postprint 40 p, 2.2 MB

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