Cr/SmCo/Cr thin films with Sm concentration of 37.7 at.% were deposited on glass substrates by magnetron sputtering. Measurement of magnetic properties showed that the SmCo film possessed good magnetic anisotropy, a high coercivity of 3019 kA/m and low magnetic exchange coupling. Microstructure analysis showed that crystallized SmCo5 magnetic phase, non-magnetic SmCo2 phase and Sm2Co7 phase co-existed in the film. The non-magnetic SmCo2 phase might function as isolator of SmCo grains, leading to a decrease of magnetic exchange coupling. Moreover, a Cr2O3 oxide layer which could protect the SmCo layer from oxidation formed at the surface of the Cr cap layer.
The exchange coupling at the ferromagnetic/antiferromagnetic(FM/AFM) interface is influenced by both the magnetic structure and the crystalline micro-structure.Co/FeMn/Co thin films with 0.4 nm Pt spacer layer inserted into the Co/FeMn and FeMn/Co interface respectively were deposited by means of magnetron sputtering.The two interfaces upon and beneath the FeMn layer show distinct behaviors before and after the Pt spacer inserted.There is a remarkable shrink of the interfacial uncompensated spins within the FeMn bottom interfacial monolayers,whereas a relaxation of the pinning strength of the FeMn interfacial spins along the out-of-plane direction occurs at the top interface.XRD analysis indicates the Pt layer upon the FeMn layer forms an fcc(002) texture,implying the magnetic discrepancy between the top and bottom FeMn interfaces has crystalline structural origins.
LIU Yang,FU Yanqiang,JIN Chuan,and FENG Chun Department of Materials Physics and Chemistry,University of Science and Technology Beijing,Beijing 100083,China
The spin transport property of a ferromagnet (FM)/insulator (Ⅰ)/resonant tunneling diode (RTD) heterostructure was stud-ied. The transmission coefficient and spin polarization in a multilayered heterostructure was calculated by a Schrdinger wave equa-tion. An Airy function formalism approach was used to solve this equation. Based on the transfer matrix approach,the transmittivity of the structure was determined as a function of the Feimi energy and other parameters. The result shows that the spin polarization induced by the structure oscillates with the increasing Fermi energy of the FM layer. While the thickness of the RTD is reduced,the resonant peaks become broad. In the heterostructure,the spin polarization reaches as high as 40% and can be easily controlled by the external bias voltage.
Microstructures and magnetic properties of Ta/Pt/Co 2 FeAl(CFA)/MgO multilayers are studied to understand perpendicular magnetic anisotropy(PMA) of half-metallic full-Heusler alloy films.PMA is realized in a 2.5-nm CFA film with B2-ordered structure observed by a high resolution transmission electron microscope.It is demonstrated that a high quality interface between the ferromagnetic layer and oxide layer is not essential for PMA.The conversions between in-plane anisotropy and PMA are investigated to study the dependence of magnetic moment on temperature.At the intersection points,the decreasing slope of the saturation magnetization(M s) changes because of the conversions.The dependence of M s on the annealing temperature and MgO thickness is also studied.
Zn0.99Cu0.01O films were studied experimentally and theoretically.The films were prepared by pulsed-laser deposi tion on Pt(111)/Ti/SiO2/Si substrates under various oxygen pressures to investigate the growth-dependence of the ferromag netic properties.The structural,magnetic,and optical properties were studied,and it was found that all the samples possess a typical wurtzite structure,and that the films exhibit room-temperature ferromagnetism.The sample deposited at 600℃and an oxygen pressure of 10 Pa showed a large saturation magnetization of 0.83μB/Cu.The enhanced ferromagnetism in the(Cu,Li)-codoped ZnO is attributable to the existence of Zn vacancies(VZn),as shown by first-principles calcu lations.The photoluminescence analysis demonstrated the existence of V Zn in both Zn0.99Cu0.01O and(Cu,Li)-codoped ZnO thin films,and this plays an important role in the increase of ferromagnetism,according to the results of first-principles calculations.
The current-driven domain wall motion was investigated on permalloy nanowires with different dimensions by micromagnetic simulations.The critical current density increased with the reduction in both the width and thickness of nanowires because of the enhanced hard-axis anisotropy.At a thickness of 5 nm,the critical current density decreased with the reduction of the nanowire width because of the reduced domain wall width.
Co2FeAl0.5Si0.5 (CFAS)-based multilayers sandwiched by MgO layers have been deposited and annealed at different temperatures. Perpendicular magnetic anisotropy (PMA) with the magnetic anisotropy energy density Ku ≈2.5×106 erg/cm3 (1 erg = 10-7 J) and the coercivity Hc = 363 Oe (1 Oe = 79.9775 A · m-1) has been achieved in the Si/SiO2/MgO (1.5 nm)/CFAS (2.5 nm)/MgO (0.8 nm)/Pt (5 nm) film annealed at 300 ℃. The strong PMA is mainly due to the top MgO layer. The structure can be used as top magnetic electrodes in half-metallic perpendicular magnetic tunnel junctions.
