Shubnikov-de Haas effect in Bismuth in high magnetic fields

Shubnikov-de Haas effect in Bi was observed in pulsed high magnetic fields up to 420 kG. Hole resonances were observed up to the second (N = 1) and the third (N = 2) peaks for the magnetic fields along the bisectrix and the binary axes, respectively. From the analysis of the resonant magnetic fields, changes of the Fermi level and the carrier concentration were calculated. The field at which the semimetal to semiconductor transition will occur was estimated as 850 kG ∽ 1 MG for the field direction parallel to the binary axis. Anomalously large decrease of the magnetoresistance was observed above 300 kG.     

Zeeman effect measurements in SO2: An internal magnetic field calibrant

It is proposed that the Zeeman effect of the 2₀₂ → 1₁₁ transition in sulfur dioxide be used as a magnetic field calibration standard. The recent accurate beam maser measurements on this transition by Ellenbroek and Dymanus have been confirmed by electric resonance measurements in the 1₁₁ level. The Zeeman splittings most useful for calibration purposes depend linearly on the magnetic field. For perpendicular selection rules the Zeeman coefficient is 0.5282(3) MHz/kG while parallel transitions have a 0.3722(3) MHz/kG Zeeman coefficient. The sign of the rotational magnetic moment of SO₂ has been determined to be negative.     

Nuclear magnetic resonance of oriented54Mn nuclei in antiferromagnetic MnCl2 · 4H2O

Nuclear magnetic resonance of oriented⁵⁴Mn nuclei in antiferromagnetic MnCl₂ · 4H₂O has been observed. The first two lines of the sextuplet split by quadrupole interaction are at frequencies 500.4 and 514.7 MHz, implying a hyperfine field of 643(5) kG. The stronger line at 500.4 MHz has a half-width at half maximum of 60 kHz and is shifted downward and split in frequency on application of a magnetic field. The nuclear spin-lattice relaxation time is dependent both on the applied field and the size and/or quality of the crystal.     

The influence of small magnetic fields on the Mössbauer relaxation spectra of Au: Yb alloys

The influence of an external magnetic field on the hyperfine structure of the Γ₇ CEF ground state of dilute Yb impurities in Au is investigated through the Mössbauer effect. Strong changes in the shape of the hyperfine spectra are observed when small magnetic fields (?1 kG) are applied. The dependence of the hyperfine structure on applied magnetic fields is shown through a Breit-Rabi diagram. The electronic relaxation rate for this system is found to be independent of the fields applied. The nature of polarized radiation emitted by such sources is discussed.     

Measuring magnetic fields in plasmas by means of light scattering

The theory of light scattering in plasmas containing a magnetic field yields the special case of modulated scattering spectra. The modulation frequency is governed by the field in the plasma and is equal to the electron cyclotron frequency. In this investigation magnetic fields in a plasma were determined by a laser scattering experiment. The experimental data were: electron densityn _e=10¹⁶cm^?3, electron temperatureT _e=3.2 eV, scattering angle θ=90 °, scattering parameter α=0.6, and a maximum field in the plasma of 125 kG. The spectrum measured at the maximum magnetic field was modulated with 3.6 × 10¹¹ Hz. In scattering experiments with a field reduced by about 20% the observed modulation frequency was 2.8 × 10¹¹ Hz. A thermal spectrum with a smooth profile was found when no field was present in the plasma. Applying the theory of cyclotron modulated spectra one obtains from the scattering experiment magnetic fields of 128, 100, and 0 kG. Within the experimental accuracy these values agree well with the fields determined by means of magnetic probes. Other possible interpretations of the measured deviations from thermal spectra (modulation with the plasma frequency or additional cold electron components in the plasma) are discussed, but they afford no explanation. This experiment has domonstrated that magnetic fields in plasmas can be measured locally and almost without disturbance by means of light scattering.     

Magnetic properties of Europium-graphite intercalation compound C6Eu

An ordered state with a complex magnetic structure has been observed below 4CK. The magnetization for H ⊥ c (c; the c-axis) shows a field-induced phase transition from a small magnetic moment state ( ～ 0.6μ_B) at lower fields to a larger moment one ( 2.2 - 2.5μ_B) above 25kG. The transition field depends on temperature and is found to be 5 - 2kG. The magnetization for H//c has only a sublinear field dependence. Above 40K the magnetic susceptibility obeys the Curie-Weiss law with θ = +1.3K and the molar Curie constant C_m = 6.78, which suggests that Eu ion is divalent in C₆Eu.     

Splitting of the electromagnetically induced transparency resonance on 85Rb atoms in strong magnetic fields up to the Paschen-Back regime

Electromagnetically induced transparency (EIT) resonance in strong magnetic fields of up to 1.7 kG has been investigated with the use of a 30-??m cell filled with an atomic rubidium vapor and neon as a buffer gas. The EIT resonance in the ?? system of the D₁ line of ⁸⁵Rb atoms has been formed with the use of two narrowband (??1 MHz) 795-nm diode lasers. The EIT resonance in a longitudinal magnetic field is split into five components. It has been demonstrated that the frequencies of the five EIT components are either blue- or red-shifted with an increase in the magnetic field, depending on the frequency ??_P of the probe laser. In has been shown that in both cases the ⁸⁵Rb atoms enter the hyperfine Paschen-Back regime in magnetic fields of >1 kG. The hyperfine Paschen-Back regime is manifested by the frequency slopes of all five EIT components asymptotically approaching the same fixed value. The experiment agrees well with the theory.     

The temperature dependence of the magnetic hyperfine field of tantalum in dysprosium

The temperature dependence of the magnetic and electric hyperfine interactions at the site of ¹⁸¹Ta impurities in polycrystalline Dy has been measured between 4.2 and 178 K using the time differential perturbed angular correlation technique. The value of the magnetic hyperfine field at 4.2 K is: |H_hf(TaDy)| = 212(9) kG The temperature dependence of the magnetic hyperfine field follows closely the prediction of the molecular field model.     

The magnetic hyperfine field at Cd nuclei in the rare earth ferromagnets Gd,Tb, Dy,Ho, Er and Tm

The time differential perturbed angular correlation technique has been used to study the combined magnetic and electric hyperfine interactions at the site of a¹¹¹Cd impurity in the rare earth ferromagnets Gd, Tb, Dy, Ho, Er, and Tm at 4.2 °K. The following magnetic hyperfine fields at the site of¹¹¹Cd have been found: ¦H _hf ¦=340(7) kG in Gd, 275 (5) kG in Tb, 221 (4) kG in Dy, 116 (3) kG in Er and 60 (6) kG in Tm. In Ho two magnetically different sites were observed with magnetic fields of 159 (3) and 139 (3) kG. Both sites are equally populated. The coupling constantJ _5f of the conduction electron-4f interaction has been calculated for the different rare earth metals from the measured hyperfine fields by means of the RKKY theory.     

Structure and electrical properties of polyaniline synthesized in presence of low magnetic field

Chemical polymerization of aniline is carried out in the presence of low magnetic field (1 kG and 2 kG). The impact of application of magnetic field externally during polymerization increases the electrical conductivity by two orders of magnitude. This enhanced electrical conductivity depends on ordering of polymer chain, structure, molecular weight, magnetic susceptibility, and thermal characteristics of polyaniline which has been studied and reported.     

High critical magnetic field superconductor La3S4

We report electrical conductivity, specific heat and magnetization measurements on La₃S₄ single crystals. The results show, that La₃S₄ is a strong coupling superconductor with a BCS coherence length of 132 Å. This extremely low value makes La₃S₄ an intrinsic high critical magnetic field superconductor with a Landau-Ginsburg parameter κ₀ of 20. For the temperature gradient of the upper critical magnetic field at the transition temperature we find values up to 35 kG/K.     

HL-2M中性束负离子试验源磁场位形及引出结构模拟分析

采用CST电磁工作室和粒子工作室软件对负离子试验源的会切磁场、过滤磁场、电子偏转磁场的位形及引出束流的光学进行了模拟计算。通过扫描会切磁体、过滤磁体、电子偏转磁体的表面磁场参数,确定了最佳的磁体结构和运行参数：周边6圈会切磁体,会切磁体表面磁场4kG,过滤磁体表面磁场5.5kG,电子偏转磁体表面磁场2.5kG,引出电压5~20kV,加速电压50~160kV,引出负离子束的光学性能满足NBI注入要求。     

Nuclear magnetic resonance on oriented189,191 Pt in iron

Nuclear magnetic resonance measurements have been performed for¹⁸⁹Pt and¹⁹¹Pt oriented at 7 and 15 mk in iron host. The magnetic hyperfine splitting frequencies, ν=¦μB_HF/Ih¦, of the¹⁸⁹Pt and¹⁹¹Pt ground states were determined to be 277.61(5) and 319.88(3) MHz. With the hyperfine field of B_HF=-1280(26) kG the nuclear magnetic moments were deduced to be: ¦μ(¹⁸⁹Pt;3/2^?)¦=0.427(9) μ^N; ¦μ(¹⁹¹Pt,3/2^?) ¦=0.492(10) μ_N. The effective spinlattice relaxation time for¹⁹¹PtFe at 7 mK in a polarizing magnetic field of 2 kG has been found to be 30(2) s using a single-exponential fit.     

Defect induced magnetic interactions in highly oriented pyrolytic graphite (HOPG): a local investigation using TDPAD method

We performed microscopic studies of the magnetic interaction in HOPG by measuring the hyperfine field of ¹⁹F using the time differential perturbed angular distribution (TDPAD) technique. The results show two hyperfine fields (B_hf) components: one varying strongly with temperature and saturating around 5 kG, while the other showing a maximum of 0.85 kG. The temperature dependence of B_hf does not show any signature of ferromagnetic ordering, but is reminiscent of enhanced paramagnetism.     

HL-2M装置低温冷凝泵在抽气工况下的热负荷分析

采用理论计算和有限元实体模型的方法,对HL-2M装置低温冷凝泵及与其相连接的真空穿透结构进行了温度分布和液氦管热负荷分析。结果显示,低温冷凝泵中液氦管的热稳态热负荷为5.45W,粒子沉积的热负荷为75.68W,真空穿透部分的热负荷为5.04W。所得结果为后续的热应力分析、低温泵流速控制和低温系统的设计提供了参考。     

Magnetic field dependence of conductance and conduction noise of an artificial grain boundary junction in a La0.67Ba0.33MnO3 epitaxial thin film

A single artificial grain boundary in La_0.67Ba_0.33MnO₃ (LBMO) thin film has been prepared by depositing the film on a bicrystal substrate using laser ablation technique. We investigated the magnetic field dependence of magnetoresistance and conductance-voltage characteristics of the grain boundary at 77 K. A decrease of nonlinearity of current-voltage characteristics was observed upon application of magnetic field. The results are explained by assuming the presence of two different types of parallel conducting channels (metallic and highly resistive) across the grain boundary. The analysis of the results reveals that the application of magnetic field suppresses magnetic disorders at the grain boundary region and increases metallic conduction channels across the grain boundary. The temperature dependence of the conduction noise of the bicrystal grain boundary was measured at 0 and 1.5 kG magnetic field and compared with a microbridge on the LBMO film having no grain boundary. The presence of the grain boundary was found to enhance noise by one order of magnitude. The noise of a bicrystal grain boundary showed a decrease in the presence of 1.5 kG magnetic field for T<210 K. This decrease of noise confirms that the application of a magnetic field induces more metallic channels across the grain boundary.     

Induced neutron magnetic form factor of LaSn3

Polarized neutron scattering techniques have been used to study the spatial distribution of the magnetization induced in a single crystal of LaSn₃ by a magnetic field of 42.5 kG at 100 K. We find that the magnetic form factor decreases very rapidly with increasing scattering angle, and bears no resemblance to the spin or orbital free-atom magnetic form factor. The experimental results are in reasonable agreement with band theoretical calculations of the spin magnetic form factor of LaSn₃. We conclude that (a) the spin part is the dominant contribution to the bulk susceptibility of LaSn₃ and (b) there is a substantial amount of Sn-5p electronic character in the wavefunctions near the Fermi level.     

Decoupling experiments for the study of electric and magnetic hyperfine interactions in ferromagnetic compounds

The decoupling experiments involving the time-differential perturbed angular correlation (TDPAC) of the 133–482 keV γ-γ cascade in the presence of an external magnetic field applied along the quantization axis have been performed to measure the electric quadrupole and the magnetic hyperfine interactions experienced by the¹⁸¹Ta nuclei at Hf sites in the pseudobinary compounds HfFe_2-xSi_x, withx=0.1 andx=0.3. The hyperfine magnetic fields measured at 298 K areH _hf=133.1±12.0 kG in the cubic (C15) Laves phase compound HfFe_1.9Si_0.1 andH _hf=76.8±7.0 kG in the hexagonal (C14) Laves phase compound HfFe_1.7Si_0.3. The decoupling technique has also been used to obtain a —ve sign for the hyperfine field experienced by¹⁸¹Ta nuclei at the Ti or Hf sites in the Heusler compound Co₂Ti_0.8Hf_0.2Sn and a+ve sign for the hyperfine field at Zr sites in the cubic (C15) Laves phase compound ZrFe₂.     

Microstructure and soft magnetic properties of CoFeZrO thin films

Nanogranular CoFeZrO thin films were successfully prepared by radio frequency reactive magnetron sputtering in O₂/Ar atmosphere. The magnetic properties and microstructure were investigated. It is found that the Co_17.08Fe_49.76Zr_16.24O_16.91 films show the best soft magnetic properties: magnetic coercivity of 0.3 Oe; anisotropy field of 44.9 Oe; saturation magnetization of 16.8 kG; electrical resistivity of 462.8 μΩ cm. The effective permeability of the films reaches 800 and flattens up to 2 GHz.     

The magnetic hyperfine field at181Ta impurities in the 4f-ferromagnets Ho and Er

The magnetic hyperfine fieldH _hf at¹⁸¹Ta impurities in the ferromagnetic Rare Earth metals Ho and Er has been determined by time differential perturbed angular correlation measurements at 4.2 K. The results |H _hf(TaHo)|=101(8)kG |H _hf(TaEr)|= 94(8)kG together with the previously determined values ofH _hf(TaGd) andH _hf(TaDy) show that the magnetic hyperfine field at Ta impurities in the Rare Earth metals is predominantly due to the conduction electron polarization of the hosts.