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1.
Using the high spin asymmetry in inverse photoemission of the Ni d-band just above the Fermi level as an indicator of surface magnetization, we have measured hysteresis curves of the (110) surface of nickel. Nearly rectangular hysteresis loops indicate a well-defined behavior of the surface magnetization of the picture-frame single crystal with sides along 110 directions. The influence of geometrical order and chemisorption of O, S, and CO on the shape of the hysteresis loops has been investigated. We found a significant reduction of the coercive force (about 10%) if the clean high-quality (110) surface is disordered on an atomic scale by ion bombardment or low-coverage chemisorption.  相似文献   

2.
Application of conversion electron Mössbauer spectroscopy (CEMS) to structural and magnetic analysis of ultrathin films and their interfaces is reviewed. Fe(110) films were prepared on W(110) under UHV conditions and analyzed in situ. CEMS provides detailed information on the mode of growth and film structure and on magnetic hyperfine fields, B hf. Local structure of B hf across the film is discussed in relation to modifications of magnetic order caused by the finite (including monolayer) film thickness and by the electronic structure of the interface.  相似文献   

3.
Giant low temperature intrinsic magnetic hardness is observed in structurally homogeneous CaCu5 type compounds RFe5−x Ni x . In SmFe5−x Ni x , this magnetic hardness peaks approximately at a composition SmFe0.2Ni4.8, with an extrapolated coercive force of 230 kOe at absolute zero. The transition metal sublattice is not anisotropic. Thus, the rare earth alone creates giant coercivity. Only compounds withc-axis preference exhibit substantial magnetic hardness (Sm, Er, Tm). Partial substitution of a tetravalent rare earth to produce crystal field anisotropy fluctuations apparently increases coercivity somewhat in the axis-preference compound SmFeNi4, but has no effect in the plane-preferred compound TbFeNi4.  相似文献   

4.
The modifications in electrical and magnetic properties of polycrystalline bulk La0.7Ca0.3Mn1−xTxO3 (T=Fe, Ga) samples at relatively higher doping concentration (x=0.08-0.12) are investigated. All the synthesized, single phase samples were subjected to resistivity measurements in the temperature range 50-300 K. No insulator-metal transition (TP) was observed for Fe doped samples with x=0.12. For all the other samples the transition temperature decreased with increase in doping concentration. The small polaron hoping energy was found to increase, rather slowly, with increase in doping concentration. The effect on magnetic properties is also prominently observed with respect to doping element and doping concentration. Interestingly, with the increase in doping concentration, the Curie temperature (TC) and TP separate out significantly indicating decoupling of electric and magnetic properties. Changes in these properties have been analyzed on the basis of magnetic disorder introduced in the system due to the magnetic and nonmagnetic nature of these ions rather than strong lattice effects which is insignificant due to similar ionic radii of Fe+3 and Ga+3 when compared to that of Mn+3.  相似文献   

5.
6.
The first order magnetic phase transition in polycrystalline sample of dysprosium (Dy) has been investigated in detail by dc-resistance vs. temperature (R-T) measurements. Distinct signature of coexistence of two magnetically ordered phases (i.e. ferromagnetic and antiferromagnetic), originating as a result of the metastable behavior associated with the first order phase transition (FOPT) is found near 90 K. By successfully recording the minor hysteresis loops within the hysteretic R-T regime of Dy, a varying degree of phase coexistence in the FOPT is demonstrated.  相似文献   

7.
Using low-temperature (5 K) spin-polarized scanning tunneling microscopy, we have studied the morphology and magnetic properties of monolayer (ML) and double layer (DL) thick Fe nanowires grown by step flow on a Mo(110) single crystal. Magnetic contrast has been obtained using tungsten tips covered by Au/Co thin films. We find that the DL Fe nanowires, similarly to ML Fe nanowires, are perpendicularly magnetized. Because of the dipolar coupling, separated DL Fe nanowires are antiferromagnetically coupled. DL wires that are touching at step edges are ferromagnetically ordered due to direct exchange coupling. We measured the widths of the magnetic domain walls in the ML and DL Fe nanowires. The domain wall width increases with the thickness of Fe.  相似文献   

8.
The concentration dependence of the specific magnetic moment value at room temperature in dilute semiconductor titanium oxides doped with either Co or Fe has been investigated. This value was found to increase sharply at small concentrations of magnetic impurity. The magnetic moment of 22.9 μB per impurity atom has been revealed for TiO2 doped with 0.15 at% Co, not yet reported in any semiconductor oxide systems. We conclude the observed giant magnetic moments are caused by the crystal lattice polarization at small impurity concentrations. The comparison with published data point to different types of the magnetization concentration dependence for various semiconductor matrixes that is probably related to the dielectric permittivity of the environment.  相似文献   

9.
10.
The phenomenon of giant intrinsic magnetic hardness is investigated in compounds R1−x Sm x Co2Ni3 with R=Y, Pr, Gd, Tb, Er. Partial Er substitution for Sm actually increases magnetic hardness while all other substitutions decrease magnetic hardness. The strength of coercivity is thus dependent on both the sign and magnitude of the crystal field interaction. The temperature dependence of coercivity is complex in the case of Pr substitution as a result of competing effects from thermal activation and a decrease in anisotropy at low temperatures. This study has been supported by a grant from the National Science Foundation.  相似文献   

11.
Fe polycrystalline nanowires were electrodeposited in nanoporous anodized alumina membranes. Their magnetic properties were studied at 10 K. The behavior of the isothermal remanence MrMr and the demagnetization remanence MdMd was determined. The corresponding ΔMΔM plot revealed the character demagnetizing of the dominant interactions. A simple analysis suggests that curling is the reversal magnetization mode in these samples. The forms of the Mrev(Mirr)HiMrev(Mirr)Hi curves were different from those encountered until now, and it seems that these forms are associated with the curling reversal mode.  相似文献   

12.
The magnetic structure of BaFe12O19 is imaged with a scanning tunneling microscope having a flexible, magnetic tip. We find that Fe thin films evaporated on a silicon tip, integrated with a cantilever, behave as magnetically soft tips. Therefore, we are able to image domain walls with high lateral resolution. A different contrast along the domain wall due to surface magnetic charges is observed. We explain the data using previously established models for wavy domain walls. The obtained images are the first experimental evidence of magnetic charges induced on the wavy domain walls in BaFe12O19.  相似文献   

13.
A new spin-density-wave (SDW) system with magnetic impurities (TMTSF)2(AsF6)1−x(FeCl4)x was prepared and its magnetic properties were studied by means of magnetization and electron-spin-resonance measurements. The anisotropic g-value and comparison of the Fe concentration with the Curie constant indicate that the Fe3+ ions are in a low-spin state. We also found that the magnetization curve of the impurity spins in this compound shows an anomalous behavior. This behavior can be explained if one assumes a field-dependent magnetic interaction between the Fe3+ spins and the SDW moment. We suppose that the field dependence of the SDW pinning potential is responsible for this phenomenon.  相似文献   

14.
The in-plane density of phonon states of clean Fe(110) surface was measured separately for the first, second, and further atomic monolayers using nuclear inelastic scattering of synchrotron radiation. The results show that atoms of the first layer vibrate with frequencies significantly lower and amplitudes much larger than those in the bulk, and that vibrational spectra along two perpendicular in-surface directions are different. The vibrations of the second layer are already very close to those of the bulk. The good agreement of the experimental results and the first-principles calculations allows for detailed understanding of the observed phenomena.  相似文献   

15.
The experimental value of the spontaneous magnetic moment μ(0) at OK of Zn2Y is 8% lower than the theoretical one. This reduction of the moment is ascribed to a local spin reversal on octahedral 3b-sites due to a high Zn-concentration in the S-block.  相似文献   

16.
The distribution functions of magnetic recording particulate tapes were studied by the measurements of magnetoremanence. For fitting distribution function, cosines series function such as Legendre polynomial has been popularly used, however, Gaussian function is found to be preferable for sharp or wide distributions. Audio metal tape has the sharpest distribution function among the seven tapes.  相似文献   

17.
In order to make clear the origin of magnetic anisotropy of amorphous alloys produced by a single roller quenching method, the composition dependence of the in-plane magnetic anisotropy of cold-rolled and as-quenched amorphous (Fe1 x Ni x )78Si10B12 alloy systems was studied at room temperature. The twofold in-plane magnetic anisotropy constantK u of cold rolled and as-quenched specimen decreases with increase inx at the Fe-rich side, and increases drastically at aboutx=0.2. Beyondx=0.25,K u decreases gradually with further increase inx. From this study, it is emphasized that there is a clear correspondence between the atomic ratio of Fe to Ni at which the anomaly in magnetic anisotropy of the amorphous alloy occurs and the position of the fcc/bcc phase boundary in the Fe−Ni metal alloy system.  相似文献   

18.
Ultrathin epitaxial FCC-Co films, which form part of a spin-valve structure, were found to undergo one- or two-jump magnetic switching, in GMR and MOKE measurements depending upon the field orientation. The transitions are mediated by the propagation of 180° or 90° domain walls. The Co two-jump spin switching in the spin-valve structure has contributed to the formation of three stable GMR states: parallel, antiparallel and a new intermediate state.  相似文献   

19.
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 Br=∼1.06 T, HC=∼371 kA/m, and (BH)max=∼160 kJ/m3 were obtained under the optimized parameters for sputtering.  相似文献   

20.
The electric field gradients measured at the surface of Fe(110) using in situ monolayer probe conversion electron Mössbauer spectroscopy were interpreted using a simple model. The spatial oscillation of the electric field gradient near the surface, which is observed experimentally, is also predicted by the calculations.  相似文献   

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