共查询到20条相似文献,搜索用时 546 毫秒
1.
Kewei Liu Dezhen Shen Xiaojie Wu Binghui Li Youming Lu 《Solid State Communications》2006,140(1):33-37
Thin iron films have been grown on (001) GaAs substrates by low pressure metal organic chemical vapor deposition (LP-MOCVD) at different temperatures with the pressure of 150 Torr. X-ray diffraction (XRD) analysis showed that all films have only one strong diffraction peak (110). The surface of Fe film became smooth with increasing the growth temperature. Magnetization measurements showed that the Fe films grown at different temperatures were ferromagnetic with easy axis parallel to the film surface and hard axis perpendicular to the substrates. The field dependence of magnetization along two axes showed a remarkable difference, implying that the samples have strong magnetic anisotropy. Furthermore, when the applied magnetic field is perpendicular to the Fe surface, a sharp jump in the hysteresis loop could be observed, followed by a broad shoulder, which is related to the interface effect, the existence of carbon and the formation of 180°/90° magnetic domains. 相似文献
2.
A model to describe the magnetic properties of Fe/Cr/Fe films with nanometer-thick layers of Fe and Cr is proposed. The model rests on the assumption that there exists a magnetic order of the linearly polarized spin-density wave type in a chromium interlayer with thicknesses even less than its wavelength. This only assumption proved to be enough to describe the following characteristics, experimentally observed, of the magnetic properties of the multilayer Fe/Cr films: the existence of short and long periods, dependences of their magnetic properties on the chromium layer thickness, noncollinear orientation of the magnetizations of neighboring iron layers, the existence of the magnetization curves beyond the hysteresis loops of magnetization. 相似文献
3.
The spin wave excitation and its size effect has been studied in Al-capped Fe films grown on low-symmetry GaAs(1 1 3)A substrates. The temperature dependence of saturation magnetization follows an effective Bloch's law as long as magnetization remains larger than about 70% of its saturation value. A significant increase of the spin wave parameter B is found in Al-capped ultrathin Fe films grown on GaAs(1 1 3)A compared to bulk Fe, Fe films on GaAs(0 0 1) and other systems. This is explained as a result of the reduction in uniaxial magnetic anisotropy observed in this orientation for the same thickness range. However, this observed uniaxial magnetic anisotropy is found to be a likely reason for stabilizing the ferromagnetism. 相似文献
4.
The magnetic phase diagram of the Fe/Cr/Fe three-layer structure with almost ideal interlayer boundaries was constructed. The effective interlayer interaction in this structure was described by the “half-angle coupling” model. Various system configurations were analyzed taking into account crystalline anisotropy, and the ground state of the system was determined. The behavior of the structure in an external magnetic field applied along easy and hard magnetic axes was studied. The magnetization curves M(H) characteristic of structures with various interface roughness parameter and interlayer exchange values were described and analyzed. The experimental situation is discussed. 相似文献
5.
We determine the minimal domain structure for the equilibrium thickness of stripes as well as for the minimal energy of the domain configuration in ultrathin films of ferromagnetically coupled spins, where the easy direction of magnetization is perpendicular to the film. It is found that the equilibrium thickness of stripes and walls depend on the exchange energy. The normalized anisotropy, f, depends on interplay between the magnetic and anisotropy energies and is almost independent of the exchange energy inside the wall. The results are compared with the experimental data for thin Ag/Fe/Ag (0 0 1) films and a good coincidence is obtained between both results. 相似文献
6.
The magnetic anisotropy of epitaxial 300 Å thick Fe films on Ag and Ag/Cr buffer layers on MgO(001) has been studied by ferromagnetic resonance and magneto-optic Kerr effect measurements. The samples were grown by molecular beam epitaxy at ambient temperature. A reduction of the effective magnetization for the samples with a Ag buffer layer is attributed to strain and dislocation formation as seen from X-ray diffraction measurements at low and high angles. In the samples with a Cr seed layer, a higher magnetic anisotropy is found which correlates with a reduced roughness. 相似文献
7.
The peculiarities of nuclear-resonance reflectometry (NRR) for different types of magnetic ordering in multilayers are considered. The theory of NRR for noncollinear magnetic structures is briefly presented. Model calculations are carried out for the [57Fe(8Å)/Cr(20 Å)]30 structure, in which the magnetization varies with depth in different ways. The results show that the “magnetic” maximum on the NRR curve occurs only when the directions of the hyperfine fields in adjacent iron layers have different projections on the synchronous beam direction. Spiral alignment of the multilayer magnetization causes the emergence of satellites near the Bragg maximum, while the “magnetic” maximum does not occur. With more complicated magnetic ordering profiles the characteristic features of available experimental curves can be explained. 相似文献
8.
C.E. Rodríguez Torres L. Errico F. Golmar A.M. Mudarra Navarro A.F. Cabrera S. Duhalde F.H. Sánchez M. Weissmann 《Journal of magnetism and magnetic materials》2007
Transparent pure and Fe-doped SnO2 thin films were grown by pulsed laser deposition technique on LaAlO3 substrates. X-ray diffraction shows that the films are polycrystalline and have the rutile structure. Surprisingly, the pure film presents magnetic-like behavior at room temperature with a saturated magnetization of almost one-third of the doped film (∼3.6 and 11.3 emu/g, respectively) and its magnetization could not be attributed to any impurity phase. Taking into account the magnetic moment measured in the pure film, the effective contribution of the impurity in the doped one can be inferred to be ∼2 μB per Fe atom. A large magnetic moment was also predicted by an ab initio calculation in the doped system, which increases if an oxygen vacancy is present near the Fe impurity. 相似文献
9.
The magnetic anisotropy field in thin films with in-plane uniaxial anisotropy can be deduced from the VSM magnetization curves
measured in magnetic fields of constant magnitudes. This offers a new possibility of applying rotational magnetization curves
to determine the first- and second-order anisotropy constant in these films. In this paper we report a theoretical derivation
of rotational magnetization curve in hexagonal crystal system with easy-plane anisotropy based on the principle of the minimum
total energy. This model is applied to calculate and analyze the rotational magnetization process for magnetic spherical particles
with hexagonal easy-plane anisotropy when rotating the external magnetic field in the basal plane. The theoretical calculations
are consistent with Monte Carlo simulation results. It is found that to well reproduce experimental curves, the effect of
coercive force on the magnetization reversal process should be fully considered when the intensity of the external field is
much weaker than that of the anisotropy field. Our research proves that the rotational magnetization curve from VSM measurement
provides an effective access to analyze the in-plane anisotropy constant K
3 in hexagonal compounds, and the suitable experimental condition to measure K
3 is met when the ratio of the magnitude of the external field to that of the anisotropy field is around 0.2.
Supported by the National Natural Science Foundation of China (Grant Nos. 90505007 and 10774061)
Recommended by LI FaShen 相似文献
10.
J. C. Walker 《Hyperfine Interactions》1985,25(1-4):419-425
Theoretical studies have investigated the temperature dependence of the magnetization at the surface of ferromagnets. For
isotropic exchange uniform throughout the sample, the temperature dependence of the surface magnetization varies asM(T)/M(0)≈(1−BT
3/2) with aB factor at least twice as great as the bulk value. For cases in which the exchange interaction is different in the surface
layer, or in which there is a significant surface exchange anisotropy, a different temperature dependence may result. These
theoretical results have seen little experimental test. We report here measurements made on epitaxial (110) Fe films in which
different temperature dependences are found depending upon the interfacial material chosen as a covering layer. 相似文献
11.
《Solid State Communications》2006,137(1-2):41-43
We report on the structural, magnetic, and magnetotransport characteristics of Cr-doped indium tin oxide (ITO) films grown on SiO2/Si substrates by pulsed laser deposition. Structural analysis clearly indicates that homogeneous films of bixbyite structure are grown without any detectable formation of secondary phases up to 20 mol% Cr doping. The carrier concentration is found to decrease with Cr ion addition, displaying a change in the conduction type from n-type to p-type around 15 mol% Cr doping. Room temperature ferromagnetism is observed, with saturation magnetization of ∼0.7 emu/cm3, remnant magnetization of ∼0.2 emu/cm3 and coercive field of ∼30 Oe for 5 mol% Cr-doped ITO. Magnetotransport measurements reveal the unique feature of diluted magnetic semiconductors, in particular, an anomalous Hall effect governed by electron doping, which indicates the intrinsic nature of ferromagnetism in Cr-doped ITO. These results suggest that Cr-doped ITO could be promising for semiconductor spin electronics devices. 相似文献
12.
I. A. Gudim A. A. Demidov E. V. Eremin D. K. Shukla 《Physics of the Solid State》2018,60(10):1989-1998
The magnetic and magnetodielectric properties of Ho0.5Nd0.5Fe3(BO3)4 ferroborate with the competing Ho–Fe and Nd–Fe exchange couplings have been experimentally and theoretically investigated. Step anomalies in the magnetization curves at the spin-reorientation transition induced by the magnetic field B ║ c have been found. The spontaneous spin-reorientation transition temperature TSR ≈ 8 K has been refined. The measured magnetic properties and observed features are interpreted using a single theoretical approach based on the molecular field approximation and calculations within the crystal field model of the rare-earth ion. Interpretation of the experimental data includes determination of the crystal field parameters for Ho3+ and Nd3+ ions in Ho0.5Nd0.5Fe3(BO3)4 and parameters of the Ho–Fe and Nd–Fe exchange couplings. 相似文献
13.
The magnetic and structural properties of epitaxial Fe films grown on Si(1 1 1) are investigated by polarized neutron reflectometry (PNR) at room temperature. The influence of different types of interfaces, Fe/Si, Fe/FeSi2 and Au/Fe on the magnetic properties of Fe films deposited by molecular beam epitaxy onto Si(1 1 1) are characterized. We observe a drastic reduction of the magnetic moment in the entire Fe film deposited directly on the silicon substrate essentially due to strong Si interdiffusion throughout the whole Fe layer thickness. The use of a silicide FeSi2 template layer stops the interdiffusion and the value of the magnetic moment of the deposited Fe layer is close to its bulk value. We also evidence the asymmetric nature of the interfaces, Si/Fe and Fe/Si interfaces are magnetically very different. Finally, we show that the use of Au leads to an enhancement of the magnetization at the interface. 相似文献
14.
Multilayered films with artificial superstructures were prepared by alternately depositing Fe and Nd in ultrahigh vacuum. The magnetic properties are studied from57Fe Mössbauer spectroscopy. The hyperfine field in Fe layers and the direction of Fe magnetic moments depend on the Fe and Nd layer thicknesses. For films with certain Fe and Nd layer thicknesses, the direction of Fe magnetic moments is in-plane at 300 K but changes to be perpendicular at low temperatures. The direction of Fe magnetic moments is discussed in relation with the magnetization of interface Nd atoms. 相似文献
15.
The magnetic anisotropy of ferromagnetic (FM) Ni, Co, and Fe polycrystalline thin films grown on antiferromagnetic (AF) FeF(2)(110) epitaxial layers was studied, as a function of temperature, using ferromagnetic resonance. In addition to an in-plane anisotropy in the FM induced by fluctuations in the AF short-range order, a perpendicular (biquadratic) magnetic anisotropy, with an out-of-plane component, was found which increased with decreasing temperature above the AF Neél temperature (T(N) = 78.4 K). This is a surprising result given that the AF's uniaxial anisotropy axis was in the plane of the sample, but is consistent with prior experimental and theoretical work. The resonance linewidth had a strong dependence on the direction of the external magnetic field with respect to in-plane FeF(2) crystallographic directions, consistent with interface magnon scattering due to defect-induced demagnetizing fields. Below T(N), the exchange bias field H(E) measured via FMR for the Ni sample was in good agreement with H(E) determined from magnetization measurements if the perpendicular out-of-plane anisotropy was taken into account. A low field resonance line normally observed at H ≈ 0, associated with domain formation during magnetization in ferromagnets, coincided with the exchange bias field for T < T(N), indicating domain formation with the in-plane FM magnetization perpendicular to the AF easy axis. Thus, biquadratic FM-AF coupling is important at temperatures below and above T(N). 相似文献
16.
Shi-Hui Ge Cheng-Xian Li Zhi-Yong Wang De-Sheng Xue Fa-Shen Li 《Hyperfine Interactions》1992,68(1-4):353-356
Fe(x)/Mo(y), multilayered thin films (MLF) with y=7.0 nm and x=0.7, 1.3, 2.6, 3.6, 13.0 nm were fabricated by radio frequency (RF) sputtering. X-ray diffraction evidences that these films have a good periodicity and bcc structure for both Fe and Mo layers. Mössbauer spectra at room temperature (RT) are used to investigate the structure and the local magnetic properties of the interfaces between Fe and Mo layers. It is found that the interfaces present alloying features, i.e. the Fe atoms are randomly substituted by Mo atoms. Magnetic anisotropy which forces magnetic moments to lie in the film plane and reduced magnetic moments in interface region were observed. The specific magnetization of the films exhibits a BT3/2 dependence with very large values of B which can be attributed to the distribution of exchange interaction in the interfaces. 相似文献
17.
FexPd1−x (x=.30, .44, .55, .67, and .78) films were directly grown on SrTiO3(001) and MgO(001) by molecular beam epitaxy at 500 C. The thickness of all films is 50 nm. X-ray diffraction shows epitaxial quality and face-center- tetragonal (00l), (002), and (003) peaks indicating an FePd L10 order state for films of x=.30, .44 and .55. X-ray diffraction only shows (002) peaks with a relatively weak intensity for the film of x=.67 and no (00l) peak is observed, but a broad body-center-cubic Fe(002) is identified for the film of x=.78. Magnetic hysteresis curves are carried out by a vibrating sample magnetometer (VSM) with an applied field within 12 kOe. Magnetization of both in-plane and perpendicular-to- the-plane measurements show a linear increase of the magnetization saturation from 560 emu/cm3 to 1250 emu/cm3 as x increasing from .30 to .78. For the results of the in-plane measurements, remanence (Mr), however, shows a minimum while the anisotropy field (Hk) shows a maximum for the film with x=.44 indicating the optimal content ratio of Fe/Pd for perpendicular anisotropy in the present alloy films. Further, negative remanence is observed in the hysteresis curves where the field is perpendicular to the film of x=.78 This may indicate that the L10order state still affects the magnetic anisotropy for high Fe content films even though the film has a body-center-cubic structure. 相似文献
18.
The evolution of ferromagnetic order in high-energy ball-milled Al–1 at% Fe before the onset of a considerable Fe–Al solid solution phase has been investigated using 57Fe Mössbauer and bulk magnetization studies. The unmilled sample does not exhibit bulk magnetic properties and an onset of bulk magnetization is observed only after 30 min of milling, when the grain size becomes comparable to the ferromagnetic exchange length. The Curie temperatures of all the samples are less than that of pure iron. The reduction in grain size is accompanied by an increase in coercivity and reduced remanence and a decrease in TC. The effective magnetic moment per iron atom decreases with the development of a non-magnetic, Al-rich Fe–Al solution on longer milling. The clustering of Fe at grain boundaries is responsible for the observed bulk magnetic ordering. The systematic variation of the magnetic properties has been qualitatively correlated with the evolution of microstructure, reduction in grain size and enhanced inter-granular exchange coupling. 相似文献
19.
Hakan Kockar Mursel Alper Turgut Sahin Oznur Karaagac 《Journal of magnetism and magnetic materials》2010,322(9-12):1095-1097
Co–Fe films were electrodeposited on polycrystalline Titanium substrates from the electrolytes with different pH levels. X-ray diffraction (XRD) was used to study the crystal structure of the films. The XRD patterns showed that the films grown at the pH levels of 3.70 and 3.30 have a mixed phase consisting of face-centred cubic (fcc) and body-centred cubic, while those grown at pH=2.90 have only fcc structure. It was observed that the film composition, by energy dispersive x-ray spectroscopy, contain around 88 at% Co and 12 at% Fe for all films investigated in this study. Morphological observations indicated that all films have grainy structure with the slight change of grain size depending on the electrolyte pH. Magnetoresistance measurements, made at room temperature, showed that all films exhibited anisotropic magnetoresistance, which is affected by the electrolyte pH. From the magnetic measurements made by vibrating sample magnetometer, the saturation magnetization increases as the electrolyte pH decreases. Furthermore, all films have in-plane easy-axis direction of magnetization. 相似文献
20.
D. Kerkmann 《Applied Physics A: Materials Science & Processing》1989,49(5):523-526
Experimental evidence is given for a four-fold in-plane magnetic anisotropy of the p(1×1) Co monolayer epitaxially grown on a Cu(001) substrate. Temperature dependent hysteresis curves show the magnetization remaining almost constant up to 400 K and the coercive field drastically increasing as the temperature is decreased. 相似文献