Magnetic properties of thin Fe layers in Fe/Au artificial superstructured films

Iron layers of monolayer thick are synthesized between thick Au layers by alternate deposition of Fe and Au metals. From⁵⁷Fe Mössbauer absorption spectroscopy, it is found that the Fe monolayer is ferromagnetic at 4.2 k. At higher temperatures, the spectra show a relaxation of the hyperfine field and above 150 K, all Fe atoms are observed as a doublet in the spectra.     

Magnetic properties of Fe/Si/Fe trilayer films

The magnetization of Fe/Si/Fe trilayer films is experimentally investigated at low temperatures. It is found that the shape of the magnetization curves measured at T<30 K depends on the thermomagnetic state of the system. The possible mechanisms of the interaction between iron layers are discussed.     

Magnetic properties and structures of Fe/MgF2 multilayered films

Multilayers composed of Fe and MgF₂ with layer thicknesses between 9 Å and 100 Å and of 30 Å, respectively, were prepared with an ultrahigh-vacuum deposition technique. Medium-angle X-ray data show that the Fe layers in the BCC phase have considerable (1 1 0) texture. Periodicity due to multilayered structures was confirmed by a small-angle X-ray diffraction study and cross-section transmission electron microscope for films with Fe layer thicknesses >45 Å. In an Fe/MgF₂(9 Å/30 Å) sample, an island structure for the Fe layers was suggested by the existence of superparamagnetism in a film. At 4.2 K, enhancements of both magnetization and hyperfine field were observed in films having Fe layers thinner than 40 Å. The maxima in the magnetization (233 emu/g of Fe) and in the average hyperfine field (390 kOe) at 4.2 K were found in an Fe/MgF₂(9 Å/30 Å) film and were approximately 105% and 115% that of the bulk α-Fe, respectively. The thickness dependence suggests a 12% enhancement in the magnetic moment of interface Fe atoms. No exchange bias was found in the films, implying that antiferromagnetic fluorides are not formed at the interface, which is different from the case of Fe/LiF and Fe/CaF₂ multilayers.     

Magnetic properties of Fe/Pt films by symmetrical insertion of Ag

Ultrathin Ag (0.5 nm) pinning layers (APLs) were symmetrically inserted into [Fe/Pt] bilayers to introduce controllable defects on the interfaces between Ag and Fe/Pt multilayers. The highest coercivity 7700 Oe and remanent squareness 0.95 were obtained with five APLs. The large enhancement in coercivity (75% increment compared with that without APL) is due to the relative uniform defects that introduced pinning effects on the interfaces between the APLs and Fe/Pt multilayers. According to the distribution of angule- dependent coercivity of Fe/Pt multilayers without and with APLs, a tendency is suggested of weakened domain-wall motion while enhanced rotation of reverse domain mode.     

Magnetic properties of Fe/ZnSe/Fe trilayers

The magnetic properties of Fe/Zn/Fe trilayers have been studied by ferromagnetic resonance and magnetization measurements. These measurements have been used to investigate the magnetic anisotropy of the iron layers and the magnetic coupling across the semiconductor spacer. The angular dependence of the resonance spectra has been measured in-plane and out-of-plane in order to deduce magnetic anisotropy constants of the samples. Experimental data were fitted by using an energy-density expression that includes bulk cubic anisotropy, growth-induced uniaxial in-plane anisotropy and perpendicular-surface anisotropy terms. A small ferromagnetic coupling is observed in the trilayers with spacer thickness up to .     

Magnetic properties of amorphous Ge–Fe thin films

Thin films of Ge_100−xFe_x (x in at%) alloys, fabricated by thermal co-evaporation, have an amorphous structure at compositions x<∼40, although an unidentified crystalline phase with an FCC symmetry also exists at low Fe content. Magnetization versus temperature curves show that saturation magnetization is non-zero (1 to 2.5 emu/cm³) and remains nearly unchanged up to the highest measured temperature of 350 K. Magnetic hysteresis loops at room temperature show a typical ferromagnetic shape, complete saturation occurring by 1–2 kOe. These results may indicate ferromagnetic ordering at room temperature. No definite tendency is observed in the compositional dependence of saturation magnetization.     

Magnetic properties of thermally deposited Fe/GaAs(100) thin films

Thin (50–200 Å) films of iron have been prepared on (100) gallium arsenide substrates by thermal evaporation at a deposition rate of 3–30 Å/s and a pressure of ～10^?5 torr. Dependences of the saturation magnetization, cubic and uniaxial planar anisotropy constants, and the ferromagnetic resonance linewidth on the film thickness were studied by ferromagnetic resonance at 9.8 GHz. It has been found that the parameters of thermally deposited Fe/GaAs (001) films are comparable to those achieved with molecular-beam epitaxy.     

Nd28Fe66B6/Fe50Co50双层纳米复合膜的结构和磁性

利用磁控溅射法制备了Nd28F66B6/Fe50Co50双层纳米复合磁性薄膜,研究了其结构和磁性.经873K退火处理15min后,利用x射线衍射仪测定薄膜晶体结构,采用俄歇电子能谱仪估算薄膜厚度和超导量子干涉仪测量其磁性.磁性测量表明,1)该系列薄膜具有垂直于膜面的磁各向异性.从起始磁化曲线和小回线的形状特征可知,矫顽力机制主要是由畴壁钉扎控制.2)对于固定厚度(10nm)层的硬磁相Nd-Fe-B和不同厚度(dFeCo=1-100nm)层软磁相FeCo双层纳米复合膜,剩磁随软磁相FeCo厚度的增加快速增加,而矫顽力则减少.当dFeCo=5nm时,最大磁能积达到160×103A/m.磁滞回线的单一硬磁相特征说明,硬磁相Nd-Fe-B层和软磁相FeCo层之间的相互作用使两相很好地耦合在一起.剩磁和磁能积的提高是由于两相磁性交换耦合所致.     

Magnetic and magnetoresistive properties of Fe10Ni90 films

We study the effect of the substrate temperature and the temperature and conditions of thermomagnetic treatment on the magnetic and electrical properties of Fe10Ni90 films deposited on single-crystal silicon substrates by ion-beam sputtering. The laws found to govern these properties are associated with the transformations of the microstructure of the films. The maximum magnetoresistance ratio is shown to occur in films deposited on slightly heated substrates and vacuum-annealed at about 500C. The coercive force, anisotropy field in the plane of the films, the density of bonds at domain walls, and the magnetoresistance ratio are determined as functions of the thickness.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 9–13, January, 1991.We thank E. I. Teitel and N. N. Schchegoleva for measuring the microstructure parameters of the films.     

Magnetic properties of Fe and Ni films evaporated in poor vacuum

To examine the pressure dependence of magnetic characteristics of Fe and Ni films, the films were prepared in vacuum ranging from 10^–5 to 10^–2 torr.Saturation magnetizationM _s ^* , perpendicular anisotropyK ^* and coercive forceH _c for Fe and Ni films deposited at around 10^–5 torr were in good agreement with the values obtained by others. When the film thickness was less than 500 ,M _s ^* for Fe films increased with pressure, while it decreased monotonically for Ni films. At pressures between 2×10^–3 and 10^–2 torr,M _s ^* decreased rapidly for Fe but it increased slightly for Ni. This interesting behaviour was most marked with film thickness of about 500 . Corresponding to the change inM _s ^* , bothK ^* andH _c also changed with deposition pressure.The result should be explained in terms of the presence of Fe₄N, Fe₈N and Ni₃N, as well as the macroscopic and microscopic structures of films.     

Magnetooptical properties of Fe/Pd multilayer films

Multilayer films of Fe(x)/Pd(30 Å) (6≤x≤30 Å) are investigated with the help of the transversal Kerr effect (TKE) with incident light in the energy range 1.3–3.6 eV. Oscillations of the TKE depending on the thickness of the iron layer are revealed. The off-diagonal element of the dielectric tensor ? ₂ ^′ is calculated using themeasured values of the TKE for two incidence angles of light and the optical constants of all samples. It is shown that the quantity ? ₂ ^′ ω² (where ω is the frequency of incident light), which is proportional to the interband density of states, also oscillates, and its oscillations are similar in character to oscillations of the Kerr effect. The observed oscillatory dependence of the TKE and of the interband density of states are related to the manifestation of quantum confinement effects.     

Magnetic properties of nanostructured spinel ferrites and nanocomposite Nd2Fe114B/α-Fe permanent magnets

This paper presents some of the important magnetic properties of the nanostructured spinel ferrites such as Ni_0.5Zn_0.5Fe₂O₄ and Mn_0.67Zn_0.33Fe₂O₄ and also that of the nanocomposite Nd₂Fe₁₄B/α-Fe permanent magnetic material. The increase in the magnetic transition temperature of Ni-Zn ferrite from 538 K in the bulk state to 592 K when the grain size is reduced to 16 nm is correlated to the enhancement in the AB superexchange interaction strength because of an increase in the magnetic ion concentration in the A-site on milling, as shown by the EXAFS and in-field Mössbauer studies. The particle size has been tailor-made by varying the concentration of the oxidant in the case of Mn-Zn ferrite. The critical particle size for the superparamagnetic limit has been found to be 25 nm with an effective magnetic anisotropy constant of 7.78 kJ m^?3 which is about an order of magnitude higher than that of the bulk ferrite. The exchange coupling is found to be strengthened in the nanocomposite magnet Nd₂Fe₁₄B/α-Fe, when the grain boundary anisotropy is removed by thermal annealing and thus facilitating the enhancement of the energy product     

Magnetic properties of Nd–Fe–B film magnets prepared by RF sputtering

Highly oriented films of ∼6 μm in thickness consisting of the Nd₂Fe₁₄B compound phase were obtained by a three-dimensional sputtering method at room temperature and the subsequent crystallization by annealing. The c-axis orientation and coercivity of film samples were sensitive to the sputtering parameters and annealing conditions. The optimum temperature and time for annealing were 650 °C and 30 min to show the highest coercivity without any deterioration for the orientation of Nd₂Fe₁₄B grains, and furthermore the degree of c-axis orientation was increased by decreasing the Ar gas pressure or input power for sputtering. The resultant film magnets with good magnetic properties of B_r=∼1.06 T, H_C=∼371 kA/m, and (BH)_max=∼160 kJ/m³ were obtained under the optimized parameters for sputtering.     

Magnetic and magnetooptical properties of Fe/Pt and Fe/Pt/Fe thin-film magnetic structures

Results of a study of magnetic and magnetooptical properties of Fe/Pt double-layer and Fe/Pt/Fe three-layer thin-film magnetic structures are presented. A strong effect of the Pt layer on magnetic properties of the studied samples was revealed. It was established that the saturation field of three-layer magnetic structures has an oscillating magnitude with varying Pt layer thickness, and the oscillation period is a function of the Fe layer thickness. The data obtained are explained by the presence of exchange interaction between the Fe layers via the Pt layer. A strong effect of Pt on spectral dependences of the equatorial Kerr effect in the thin-film structures under study is revealed.     

Magnetic and electrical properties in amorphous GeSeFe films

Amorphous GeSeFe films prepared by r.f. sputtering have shown paramagnetic, and ferromagnetic properties for the films with low and high Fe content, respectively. The temperature dependence of the electrical conductivity has indicated the variable range hopping conduction for the paramagnetic films and the metallic conduction for the ferromagnetic films. The films with intermediate Fe content have behaved intermediate between semiconductive and metallic conduction. These films are likely to be antiferromagnetic.     

Magnetic and structural properties of Fe/Cu multilayers

Fe/Cu multilayers with Fe and Cu layers of equal thicknesses were grown by high-vacuum evaporation on Si(1 1 1) substrates at room temperature. The crystal orientation, the thickness of the elemental layers and the interplanar distances were analysed by both low- and high-angle X-ray diffraction in the θ–2θ configuration. The magnetic properties of Fe/Cu multilayers were studied by both a static and a dynamic technique, namely surface magneto-optical Kerr effect (SMOKE) and Brillouin light scattering (BLS). Longitudinal SMOKE cycles permitted us to determine the orientation of the easy axis of the magnetization and to put in evidence an appreciable in-plane magnetic anisotropy in multilayers with low periodicity and highly coherent structure. Polar loops were then used to determine the out-of-plane anisotropy fields, showing that both first- and second-order contributions are to be considered in order to reproduce the hysteresis cycle. BLS was then exploited to detect thermaly excited spin waves through inelastic scattering of light. The out-of-plane anisotropy fields evaluated by this high-frequency dynamic technique compare fairly well with the first-order values obtained by analysis of polar SMOKE hysteresis cycles.     

Magnetization process of Fe layers in Fe/Nd multilayered films investigated by57Fe Mössbauer spectroscopy

The magnetization process of Fe and Nd layers at 5K in Fe/Nd multilayered films with strong perpendicular magnetic anisotropy is elucidated from a comparison of⁵⁷Fe Mössbauer spectra in the presence of the external field applied parallel to the film plane with total magnetization. At zero external field, the film has a magnetic multi-domain structure. The Nd layer moment is perpendicular to the film plane and the Fe layer moment points in the out-of-plane direction. The Fe layer moment monotonically rotates to the in-plane direction with increasing external field parallel to the film plane, while the Nd layer moment is oriented to the film normal direction up to the external field of 10kOe, above which the Nd layer moment gradually turns to the direction of the external field.