First-order reversal curve investigated magnetization switching in Pd/Co/Pd wedge film

The magnetization switching plays an essential role in spintronic devices.In this study,a Pd（3 nm）/Co（0.14–1.68 nm）/Pd（5 nm） wedge film is deposited on an Mg O（111） substrate by molecular beam epitaxy.We investigate the polar magneto-optical Kerr effect（MOKE） and carry out the first-order reversal curve（FORC） measurements.For the wedge system,it is observed that the Co thickness could drive the spin reorientation transition（SRT） from out-of-plane to in-plane.Meanwhile,we find the different types of magnetization switchings in the continuous SRT process,which can originate from the formation of different magnetic compositions.Our work provides the possibility of tuning the interfacial effect,and paves the way to analyzing magnetization switching.

Thickness dependent manipulation of uniaxial magnetic anisotropy in Fe-thin films by oblique deposition

The uniaxial magnetic anisotropy of obliquely deposited Fe（001）/Pd film on MgO（001） substrate is investigated as a function of deposition angle and film thickness. The values of incidence angle of Fe flux relative to surface normal of the substrate are 0°, 45°, 55°, and 70°, respectively. In-situ low energy electron diffraction is employed to investigate the surface structures of the samples. The Fe film thicknesses are determined to be 50 ML, 45 ML, 32 ML, and 24 ML（1 ML = 0.14 nm） by performing x-ray reflectivity on the grown samples, respectively. The normalized remanent magnetic saturation ratio and coercivity are obtained by the longitudinal surface magneto-optical Kerr effect. Here, the magnetic anisotropy constants are quantitatively determined by fitting the anisotropic magnetoresistance curves under different fields.These measurements show four-fold cubic anisotropy in a large Fe film thickness（50 ML） sample, but highly in-plane uniaxial magnetic anisotropies in thin films（24 ML and 32 ML） samples. In the obliquely deposited Fe films, the coercive fields and the uniaxial magnetic anisotropies（UMAs） increase as the deposition angle becomes more and more tilted. In addition, the UMA decreases with the increase of the Fe film thickness. Our work provides the possibility of manipulating uniaxial magnetic anisotropy, and paves the way to inducing UMA by oblique deposition with smaller film thickness.

Thickness-dependent magnetic anisotropy in obliquely deposited Fe(001)/Pd thin film bilayers probed by VNA-FMR

The thickness-dependent magnetic anisotropy of obliquely deposited Fe(001)/Pd thin films on Mg(001) is investigated by fitting the field-dependent resonant field curve using the Kittel equation.In this study, three Fe film samples with thicknesses of 50 monolayers(ML), 45 ML, and 32 ML deposited at 0°, 45°, and 55°, respectively, are used.The magnetic anisotropy constant obtained from ferromagnetic resonance(FMR) spectra exhibits a dominant fourfold magnetocrystalline anisotropy(MCA) at the normal deposition angle with larger Fe thickness.However, the in-plane uniaxial magnetic anisotropy(UMA) is induced by a higher oblique deposition angle and a smaller thickness.Its hard axis lies between the [100] and [010] directions.The FMR data-fitting analysis yields a precise measurement of smaller contributions to the magnetic anisotropy, such as in-plane UMA.Due to MCA, when the magnetic field is weaker than the saturated field,the magnetization direction does not always align with the external field.The squared frequency-dependent resonant field measurement gives an isotropic Landé g-factor of 2.07.Our results are consistent with previous experiments conducted on the magneto-optical Kerr effect(MOKE) and anisotropic magnetoresistance(AMR) systems.Thus, a vector network analyzer ferromagnetic resonance(VNA-FMR) test-method for finding UMA in obliquely deposited Fe(001)/Pd bilayer ferromagnetic thin films, and determining the magnetic anisotropy constants with respect to the film normal deposition, is proposed.

Manipulating magnetic anisotropies of Co/MgO(001) ultrathin films via oblique deposition

We present a systematic investigation of magnetic anisotropy induced by oblique deposition of Co thin films on MgO（001） substrates by molecular beam epitaxy at different deposition angles,i.e.,0？,30？,45？,60？,and 75？with respect to the surface normal.Low energy electron diffraction（LEED）,surface magneto–optical Kerr effect（SMOKE）,and anisotropic magnetoresistance（AMR） setups were employed to investigate the magnetic properties of cobalt films.The values of in-plane uniaxial magnetic anisotropy（UMA） constant Ku and four-fold magnetocrystalline anisotropy constant K1 were derived from magnetic torque curves on the base of AMR results.It was found that the value of Ku increases with increasing deposition angle with respect to the surface normal,while the value of K_1 remains almost constant for all the samples.Furthermore,by using MOKE results,the Ku values of the films deposited obliquely were also derived from the magnetization curves along hard axis.The results of AMR method were then compared with that of hard axis fitting method（coherent rotation） and found that both methods have almost identical values of UMA constant for each sample.