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1.
The effect of uniaxial compression on the behavior of shallow aluminum acceptor centers in silicon has been studied. The μAl impurity atoms were created by implanting negative muons into silicon single crystals doped with phosphorus to 1.6×1013 cm?3 (sample 1) and 1.9×1013 cm?3 (sample 2). The muon polarization was studied in the temperature range 10–300 K. Measurements were performed in a magnetic field of 2.5 kG oriented perpendicularly to the muon spin. The samples were oriented so that the selected crystal axis ([111] and [100] in samples 1 and 2, respectively), the magnetic field, and the initial muon-spin polarization were mutually perpendicular. External pressure applied to the sample along the indicated crystal axis changed both the absolute value of the acceptor magnetic-moment relaxation rate and the character of its temperature dependence.  相似文献   

2.
FeCoP nanocrystalline films were successfully electrodeposited on the Cu film coated silicon substrate in the bath containing Fe2+, Co2+, as well as different concentration H2PO? ions ranging from 0.001 mol/L to 0.01 mol/L. And then the samples experienced magnetic heat treatment with different heating rates. Effects of H2PO? concentration and magnetic heat treatment on morphological, structural, and magnetic properties of the films were investigated by scanning electron microscopy, X-ray diffraction, vibrating sample magnetometer, and vector network analyzer. The results suggest that the as-deposited films do not exhibit obvious in-plane uniaxial magnetic anisotropy, and interestingly after magnetic heat treatment at heating rate of 6?°C/min, the FeCoP films will possess better in-plane uniaxial magnetic anisotropy. It has been obtained that morphology and grain size play important roles in determining magnetic properties. The magnetic performance of FeCoP films with different phosphorus content can be improved by appropriate magnetic heat treatment.  相似文献   

3.
The specific heat of phosphorus doped silicon was measured at temperatures 0.1 < T < 4.2 K in external magnetic fields 0 ≦ Hext ≦ 38 kOe. The phosphorus concentration of the samples ranges from 5.3 × 1017 to 8.9 × 1018cm?3. The magnetic field dependence of the specific heat was observed in the just metallic samples as well as the non-metallic ones. The metal—non-metal transition is discussed on the basis of the Anderson localized states with correlations.  相似文献   

4.
Formation of the Si/Co interface and its magnetic properties have been studied by high-resolution photoelectron spectroscopy with synchrotron radiation. The experiments have been performed in situ in superhigh vacuum (5 × 10?10 Torr) with coating thicknesses up to 2 nm. It has been found that, in the initial stage of silicon deposition on the surface of polycrystalline cobalt maintained at room temperature, ultrathin layers of the Co3Si, Co2Si, CoSi, and CoSi2 silicides are formed. The three last phases are nonmagnetic, and their formation gives rise to fast decay of magnetic linear dichroism in photoemission of Co 3p electrons. At deposition doses in excess of ~0.4 nm Si, a film of amorphous silicon grows on the sample surface. It has been established that the Si/Co interphase boundary is stable at temperatures up to ~250°C and that further heating of the sample brings about escape of amorphous silicon from the sample surface and initiates processes involving silicide formation.  相似文献   

5.
The specific heat of ThN has been measured between 7 and 300K by an adiabatic method with continuous heating, and has been compared to that of UN. The magnetic specific heat of UN between 50 and 300K is certainly lower than that of a U4+ ions gas submitted to an octahedral crystal field of about 500 cm−1.  相似文献   

6.
The specific heat (C) of bi-layered manganites La2−2xSr1+2xMn2O7 (x=0.3 and 0.5) is investigated for the ground state of low temperature excitations. A T3/2 dependent term in the low temperature specific heat (LTSH) is identified at zero magnetic field and suppressed by magnetic fields for x=0.3 sample, which is consistent with a ferromagnetic metallic ground state. For x=0.5 sample, a T2 term is observed and is consistent with a two-dimensional (2D) antiferromagnetic insulator. However, it is almost independent of magnetic field within the range of measured temperature (0.6-10 K) and magnetic field (6 T).  相似文献   

7.
The effect of static magnetic fields on the dynamics of surface dislocation segments, as well as the diffusion mobility of a dopant in silicon single crystals, has been analyzed. It has been experimentally found that the preliminary treatment of p-type silicon plates (the dopant is boron with a concentration of 1016 cm−3) in the static magnetic field (B = 1 T, a treatment time of 30 min) leads to an increase in the mobility of surface dislocation segments. The characteristic times of observed changes (about 80 h) and the threshold dopant concentration (1015 cm−3) below which the magneto-optical effect in silicon is not fixed have been determined. It has been found that diffusion processes in dislocation-free silicon are magnetically sensitive: the phosphorus diffusion depth in p-type silicon that is preliminarily aged in the static magnetic field increases (by approximately 20%) compared to the reference samples.  相似文献   

8.
We have measured the magnetic moment of (La0.9Ba0.1)2CuO4- as a function of temperature and magnetic field and have found the onset of superconductivity at a temperature T ⋍ 35 K. From the magnetic field dependencies, we have shown that the sample is a type-II superconductor with ≲ ⋍ 11. Specific heat measurements yield a finite electronic specific heat coefficient of ∼6 mJ/mole-K2 at 4 K and a Debye temperature of only 330 K, suggesting that a strong electron-phonon interaction may be responsible for the high T in our sample.  相似文献   

9.
The magnetic phase diagram of the Fe2+ doped hexagonal ABX3 compound CsNi0.98Fe0.02Cl3 is investigated measuring the specific heat capacity and the magnetocaloric effect. In contrast to earlier specific heat, ultrasound and NMR experiments our measurements identify transitions between three ordered phases with the field applied in the hexagonal plane. Since the pure compound, a Heisenberg antiferromagnet with weak Ising anisotropy, has only two ordered phases for this field direction, while three are predicted for weak easy-plane anisotropy, our data provide the unambiguous proof that the anisotropy of CsNiCl3 can be effectively modeled by doping with Fe2+.  相似文献   

10.
Based on the analysis of the magnetostriction for Terfenol-D composites, Terfenol-D 2-2 magnetostrictive composites have been prepared with laminations perpendicular to [1 1 2] axes. Then one of the samples was annealed in the vacuum at 423 K for 15 min at the magnetic field of 240 kA/m, which is along the direction of laminations and vertical to the [1 1 2] axes of the specimen. The static magnetostriction λ and dynamic magnetostrictive coefficient d33 of samples were measured under the compressive stress of 0, 2, 4, 6 and 8 MPa. Effects of the compressive stress and the magnetic field heat treatment on the magnetostriction λ have been investigated. It is found that the magnetostriction of 2-2 composites can be improved under the compressive stress when the magnetic field is larger than 20 kA/m. The magnetostriction of 2-2 composites with the magnetic field heat treatment increases under compressive stress, and it can reach 1390×10−6 at the magnetic field of 200 kA/m and under the compressive stress of 4 MPa, much larger than the value of 860×10−6 without the magnetic field heat treatment. The highest magnetostriction of the 2-2 composite with the magnetic field heat treatment can reach 1530×10−6. The dynamic magnetostrictive coefficient d33 of 2-2 composites with the magnetic field heat treatment have been improved, compared with that without magnetic field heat treatment. The maximum value of d33 of the sample with magnetic field heat treatment is 71% larger than that without magnetic field heat treatment.  相似文献   

11.
A. Jabar 《Phase Transitions》2018,91(3):284-292
The magnetic properties and magnetocaloric effect in YMnO3 have been investigated using Monte Carlo simulations. The thermal magnetization, specific heat and magnetic entropy have been obtained for different values of exchange interactions and for a several external magnetic field values. The variation of adiabatic temperature change with the temperatures has been obtained for several values of external magnetic field. It has been found that the sample exhibited a paramagnetic to ferromagnetic phase transition at 30 K. The transition temperature of YMnO3 has been deduced for different values of size (1/L) and different values of exchange interactions. The relative cooling power with several values of external magnetic field has been established.  相似文献   

12.
Graphene/carbon composite films were prepared by electrospraying a graphene/polyacrylonitrile composite solution on SiO2-coated silicon substrates and subsequent heat treatment. The as-produced graphene/carbon composite films had a porous structure comprising graphene layers. With a magnetic field applied perpendicularly to the sample, an unexpectedly significant positive magnetoresistance attributed to e–e interaction and weak localization has been observed, which constantly increases with the magnetic field in the temperature range of 300–50 K from 0 to 80 kOe.  相似文献   

13.
The specific heat of Tb x Y1?x Sb mixed crystals (x=0, 0.103, 0.383, 0.428, 0.467, 0.635, 0.928 and 1.0) has been measured between 1.6 and 20°K using an adiabatic calorimeter. The crystal field potential is described well taking into account only 4th order terms, and the overall splitting of the ground multiplet7F6 of the Tb3+ ion has been found to be 115°K independent of the concentrationx. Forx>0.46 the specific heat curves exhibit a behaviour typical for a second order phase transition. For lower concentrations a normal Schottky anomaly is found and no evidence for magnetic order was detected. The experimental results which are in agreement with magnetic measurements are compared with molecular field calculations including crystal field and exchange interaction.  相似文献   

14.
The specific heat of single crystalline HoAl2 in magnetic fields up to 7.5 T has been measured for the temperature range 1.5–16 K. In addition the energy of a magnetic excitation in a magnetic field of 5 T at 4.2 K has been determined by inelastic neutron scattering. The results have been interpreted with a cubic crystalline electric field and an exchange interaction using the same parameter set B4=-0.85×10-4 meV, B6=+0.71× 10-6 meV and TC=31.5 K previously obtained by magnetization measurements.  相似文献   

15.
The mass spectrometry study has indicated that the magnetic field accelerates the oxidation of the surface of silicon crystals. The oxidation rate also depends on the nuclear spin of silicon: the oxidation rate of atoms with magnetic nuclei (29Si) is almost twice as high as that of atoms with spinless, unmagnetized nuclei (28Si and 30Si). Both effects—magnetic field and magnetic isotope—reliably prove that the oxidation of silicon is a spin-selective reaction involving radicals and radical pairs as intermediate paramagnetic particles. A spin-selective magnetic sensitive oxidation mechanism is discussed.  相似文献   

16.
The effect of low-energy (W = 8 keV) low-dose ((0.3?C7.3) × 102 Gy) radiation and a dc magnetic field (B = 0.17 T) on structural, micromechanical, and microplastic characteristics of silicon crystals has been studied. The features in the dynamic behavior of dislocations in silicon crystals, which manifest themselves upon only X-ray exposure and combined (X-ray and magnetic) exposure, have been revealed.  相似文献   

17.
The Pr 1-x CaxMnO3 system exhibits a ferromagnetic insulating state for the composition range x ? 0.25. A metallic ferromagnetic state is never realized because of the low hole concentration and the very small averaged A-site cation radius. In the present study, the nature of the magnetic excitations at low temperature has been investigated by specific heat measurements on a Pr 0.8 Ca0.2MnO3 single crystal. The decrease of the specific heat under magnetic field is qualitatively consistent with a suppression of ferromagnetic spin waves in a magnetic field. However, at low temperature, the qualitative agreement with the ferromagnetic spin waves picture is poor. It appears that the large reduction of the specific heat due to the spin waves is compensated by a Schottky-like contribution possibly arising from a Zeeman splitting of the ground state multiplet of the Pr3+ ions. Received 21 May 2001 and Received in final form 14 December 2001  相似文献   

18.
Temperature-dependent remanent polarization of negative muons in a silicon crystal doped with phosphorus (3.2 × 1012, 2.3 × 1015, and 4.5 × 1018 cm?3) and aluminum (2 × 1014 and 2.4 × 1018 cm?3) was examined. Measurements were made over the temperature range 4–300 K in a magnetic field of 2000 G perpendicular to the muon spin. Temperature dependence of the relaxation rate was determined for the magnetic moment of a shallow Al acceptor center in a nondeformed silicon sample, and the hyperfine interaction constant was estimated for the interaction between the magnetic moments of muon and electron shell of the muonic mAl atom in silicon.  相似文献   

19.
研究了低温下NdMnO3单晶的比热随温度和磁场的变化(2K≤T≤200K,0T≤H≤8T ).对应于 Mn磁矩亚晶格的A型反铁磁(A-AF)相变,零场下的比热曲线在85K附近出现尖锐的λ形峰,随 着磁场的增加,此λ峰降低展宽而且平滑变化,这与此温度附近磁化强度的变化规律一致. 与磁有序相变相关的熵变约为理论值的26%,这可能是由于磁有序涨落延续在较大温区造成 的.在20K以下,比热曲线出现了明显的肩膀形状的Schottky反常,其峰值随着磁场的增加而 逐渐向高温移动.考虑了低温下比热的各种贡献,根据Nd3+位有效分子场(H mf) 引起的Nd3+基态双重态(GSD)劈裂对上述现象进行了解释.通过对2K≤T≤2 0K,0T≤ H≤8T范围内比热数据的拟合,得到了样品的GSD劈裂,德拜温度和A-AF自旋波劲度系数以及 它们对磁场的依赖关系.发现GdFeO3型八面体旋转引起的A-AF结构中Mn磁矩亚晶 格的铁磁成分可能是Hmf的来源. 关键词: 比热 Schottky反常 反铁磁相变  相似文献   

20.
The specific heat of a NaNO2 sample has been measured between 2 K and 40 K in both single-domain and polydomain states. In this region the specific heat of the single domain sample follows exactly the T3 dependence. A clear excess contribution which in this temperature range has a temperature dependence between T and T2 has been detected for the polydomain sample. It is attributed to domain walls.  相似文献   

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