Coercivity enhancement in exchange biased CoO/Co₃Pt bilayers

Abstract

A study on the exchange bias effect in an hcp (0002)-textured Co 3 Pt alloy film biased by a thin CoO film is presented. The Co 3 Pt film reveals an out-of-plane easy axis of magnetization although it was grown on an amorphous silica substrate at room temperature. Similar exchange bias fields measured in in-plane and out-of-plane directions of the CoO/Co 3 Pt bilayer system were observed for maximum cooling field. Whereas a pronounced cooling field dependence of the exchange bias field is observed in-plane, it remains constant in out-of-plane direction. The temperature evolution of the coercivity and the shift of the hysteresis loop caused by the exchange bias effect are discussed in terms of thermal activation accounting for the temperature dependent competition between the interfacial exchange energy and the anisotropy energy of antiferromagnetic grains.

Perpendicular exchange bias in ferrimagnetic spin valves

“…However, for applications, perpendicular uniaxial and unidirectional anisotropies are more desirable owing to a larger thermal stability of encoded information 23 . For instance, antiferromagnets in contact to ferromagnets with perpendicular anisotropy like Co/Pt multilayers and CoPt 3 layers have been shown to exhibit EB and all other macroscopic behaviour of EB systems, like training effect, enhanced coercivity and blocking temperature for the onset of the EB [23][24][25][26] . More recently, the perpendicular EB (PEB) was demonstrated in a novel exchange-coupled system Sm 1 − 0.028 Gd 0.028 Al 2 /SmAl 2 based on the zero magnetization ferromagnet Sm 1 − 0.028 Gd 0.028 Al 2 as the pinning layer 27 .…”

Enhancement of coercivity of self-assembled stacking of ferrimagnetic and antiferromagnetic nanocubes

“…The exchange bias effect generally occurs under the field cooling (FC) conditions. 16,17,[19][20][21][22][23][24] In the present study, however, a horizontal shift of the hysteresis loop is hardly observed for the FM and AFM bilayers (Fig. S12 in the ESI †).…”

“…1,15 Recently, the coercivity and remanence of ferro-and ferrimagnetic (FM) materials have been found to be controlled by exchange coupling, such as exchange bias effects. [16][17][18][19][20][21][22][23][24][25][26] Since a combination of FM and antiferromagnetic (AFM) materials enhances the coercivity of magnetic nanoparticles and thin films, specific core-shell and layered structures have been designed to improve their magnetic properties. [16][17][18][19][21][22][23][24][25] However, precise control of the lattice constants by adjusting the preparation conditions is required to form suitable interfaces between FM and AFM materials.…”

“…[16][17][18][19][20][21][22][23][24][25][26] Since a combination of FM and antiferromagnetic (AFM) materials enhances the coercivity of magnetic nanoparticles and thin films, specific core-shell and layered structures have been designed to improve their magnetic properties. [16][17][18][19][21][22][23][24][25] However, precise control of the lattice constants by adjusting the preparation conditions is required to form suitable interfaces between FM and AFM materials. In the current work, we successfully controlled the magnetic properties through a brickwork technique using FM and AFM nanocubes as building blocks.…”