Tuning in-plane and out-of-plane exchange biases in Ni80Fe20/Cr-oxide bilayers

Abstract

The exchange bias effects of NiFe/Cr-oxide bilayers were studied. Results have shown that NiFe/Cr-oxide bilayers exhibited an exchange bias loop shift when field cooled to 5 K. A strong linear dependence of ferromagnetic NiFe and antiferromagnetic Cr2O3 thicknesses on the exchange bias field H-ex was observed. The largest interfacial exchange energy E-int similar to 5.4x10(-2) erg/cm(2) was found in bilayers with the thickest Cr2O3 layer indicating that stronger interface exchange coupling is enabled by thicker Cr2O3 layers. In addition, H-ex decreased linearly with increasing %O-2/Ar ratio, reflecting that ion-beam bombardment tends to degrade the Cr2O3 surface spin structures. We also find that annealing the Cr-oxide layer yields both a structural phase transformation and improved crystallinity, giving rise to stronger exchange bias behavior. Further, the coexistence of in-plane as well as out-of-plane exchange biases was observed in a NiFe/annealed Cr2O3/Al2O3(0001) bilayer. This clearly indicates that by using the single crystal Al2O3(0001) substrate together with a rapid thermal annealing process, the antiferromagnet Cr2O3 spins are tilted toward the out-of-plane direction and thus exhibit this unusual exchange bias behavior

Microstructural and magnetic characterization of ion-beam bombarded [Ni80Fe20-Cr]50 thin films

“…By increasing the Cr ion implantation fluence, an enhancement of the (111) peak intensity, then a lattice expansion, and eventually amorphous Ni 80 Fe 20 thin films were created, which led to a decreased Curie temperature and saturation magnetization. More recently, the exchange bias [6,7] effects of NiFe/Cr-oxide bilayers were studied by Lin and Guo [8]. The exchange bias field (H ex ) exhibited a linear dependence on the NiFe and Cr thicknesses.…”

Effects of post-deposition magnetic field annealing on magnetic properties of NiO/Co90Fe10bilayers

“…The ferromagnetic (FM)=antiferromagnetic (AF) bilayer structures have been widely investigated because understanding their mechanism is crucial for their applications in modern spintronic devices. 1,2) The microstructural and magnetic properties of the FM=AF bilayers can be altered by many techniques, such as magnetic field annealing (MFA), 3,4) ion-beam bombardment, 5,6) field cooling, 7) and so on. Among these techniques, the MFA treatment is an effective way to modify the microstructure of the bilayers, including crystallographic orientations, 8) grain sizes, 9) interlayer mixing, 10,11) etc.…”

“…Abundant published works have been reported on the interface effects of the FM=AF bilayers caused by the MFA process. 4,10,[12][13][14][15][16][17][18][19][20][21] An extended interfacial region in metal=NiO systems after annealing was exhibited due to the chemical reaction and diffusion at the interface. 10) The interface features are closely related to the interface spin configuration and thus have a considerable impact on the magnetic properties of the FM=AF bilayers.…”

Correlating Uncompensated Antiferromagnetic Moments and Exchange Coupling Interactions in Interface Ion-Beam Bombarded Co90Fe10/CoFe-Oxide Bilayers

“…The Co 90 Fe 10 (at%) / CoFe-oxide bilayers were prepared on oxidized Si wafer substrates by using a dual ion-beam sputtering deposition technique [21,22]. A Kaufman ion source (800 V, 7.5 mA) was used to focus an Argon ion-beam onto a commercial To study exchange bias effects, the Co 90 Fe 10 / CoFe-oxide bilayers were 12 kOe field-cooled from 350 to 50 K. The hysteresis loops for the films after field cooling are shown in Fig.…”

“…Exchange bias [1][2][3][4][5][6], i.e., the shift of the hysteresis loop of a ferromagnetic (FM) material in contact with an antiferromagnetic (AFM) material after a field-cooling process, depends on many factors including the particular materials involved [7][8][9][10], film growth conditions [11][12][13][14], the structural, compositional and magnetic details of the interfaces [15][16][17][18], the magnetic stiffness of the AFM moments, and the field-cooling conditions [19][20][21][22].…”