Influence of Ni-concentration on the magnetic structure in Tb(Cu,Ni)2 system

A powder sample of orthorhombic Tb(Cu_0.7Ni_0.3)₂ has been studied by neutron diffraction at T = 4.2 K and above the Curie temperature. It is found that this compound is ferromagnetically ordered at 4.2 K. The magnetic moment of Tb in this compound is (9.2 ± 0.2)μ_B, with components (2.2 ± 0.2, 0, 8.9 ± 0.1)μ_B. The influence of the Ni-concentration on the magnetic structure is discussed in the whole Tb(Cu, Ni)₂ system.     

Chemical order and magnetic properties of the Ni2−xMnSb system

The results of extensive magnetisation, X-ray and neutron powder diffraction measurements on the intermetallic compound series Ni_2-xMnSb, for 0?x?1, are reported. For x ?0.4, a high degree in the C1_b structure is observed, but for x?0.3, some disorder is evident. The series is ferromagnetic, with Curie temperatures rising from 368 to 732 K with decreasing nickel concentration. The magnetic moments all lie in the range (4.0±0.3)μ_B, with a maximum at a composition near x=0.45. The magnetic moments are largely associated with the ordered manganese sites, but it is possible that a small negative moment ?0.25μ_B may be associated with the “nickel sites” for x?0.3. This latter moment may be accounted for by disordered Mn atoms antiferromagnetically aligned.     

超薄Fe(4?)膜磁特性极化中子反射研究

Ultrathin Fe film 200  V/4  Fe/900  V/MgO（100） has been prepared by molecular beam epitaxy （MBE）. The structure parameters, such as the surface and interface roughness and the thickness of each layer, were obtained by X-ray and neutron reflectivity mea 关键词： 超薄Fe膜 磁特性 极化中子反射 分子束外延     

The paramagnetic response of a localised metallic ferromagnet

Static magnetisation and susceptibility measurements indicate that Pd₂MnSn has localised magnetic properties. This conclusion is supported by the success of the Heisenberg localised model in accounting for the spin dynamics and for the absence of spin waves in the paramagnetic phase. Polarised neutron and polarisation analysis measurements in the paramagnetic phase have established the absence of spatial magnetic correlations, and have shown the atomic moment to be (3.9 ± 0.2)μ_B per manganese atom, in close agreement with the value of (4.0 ± 0.1)μ_B obtained from static susceptibility measurements.     

The magnetic structures of HoTiO3 and ErTiO3

The magnetic structures of rare-earth titanium perovskites, ErTiO₃ and HoTiO₃, have been determined at 4.2 K by neutron diffraction. The Er³⁺ moment of (8.5 ± 0.5) μ_B lies along [001] and is colinear with the titanium moment of (-0.7 ± 0.3) μ_B. The Ho³⁺ moment of (8.1 ± 0.5) μ_B is inclined at an angle of 24° to the bc plane and 32° to the ab pla so as to produce an antiferromagnetic ordering of the x component and a ferromagnetic ordering of the y and the z components. The titanium moment of (-0.55 ± 0.3) μ_B lies in the bc plane but its precise direction has not been determined.     

Possible observation of the coexistence of superconductivity and long-range magnetic order in NdRh4B4

The ternary rare earth compound NdRh₄B₄ has been studied by means of critical field, low temperature heat capacity, and static magnetic susceptibility measurements. Features in the upper critical field and heat capacity data at 1.31 K and 0.89 K suggest the occurrence of long-range magnetic order in the superconducting state. The temperature dependence of the static magnetic susceptibility follows a Curie-Weiss law with an effective magnetic moment μ_eff = 3.58 ± 0.05 μ_B and a Curie-Weiss temperature θ_p = ?6.2 ± 1.0 K between 20 K and room temperature. However,, magnetization vs. applied magnetic field isotherms suggest the development of a ferromagnetic component in the Nd³⁺ magnetization at low temperatures.     

Neutron diffraction study of Ho(Rh0.3Ir0.7)4B4

Using powder neutron diffraction techniques, we have examined the magnetic order of the pseudoternary compound Ho(Rh_0.3Ir_0.7)₄B₄ below the Néel temperature T_N=2.7K. The magnetic structure consists of stacked antiferromagnetic basal plane sheets forming a body centered tetragonal unit cell, with a sublattice magnetization corresponding to 9.6±0.6μ_B per Ho³⁺ion at 1.5 K. Magnetic intensity versus temperature measurements indicate that the transition is second order and reveal no anomalous effects when the compound becomes superconducting at T_c=1.34K.     

Magnetic structures of dysprosium oxysulfide and dysprosium oxyselenide

The magnetic structures of Dy₂O₂S and Dy₂O₂Se have been determined by neutron diffraction experiments at 1.5 K. For these two antiferromagnetic compounds the magnetic unit cell is orthohexagonal and doubled along the c-axis. The antiferromagnetic direction is parallel to the c-axis; the values of the Dy³⁺ magnetic moment in Dy₂O₂S and Dy₂O₂Se are 7.2±0.5 μ_B and 9.0±0.5 μ_B, respectively.     

Neutron thermometry applied to magnetization and spin-lattice relaxation measurements on silver nuclei

We have studied spin-lattice relaxation in silver metal at temperatures and magnetic fields beyond the validity of the normal Korringa relation τ ₁ = κ/T _c using transmission of polarized and unpolarized neutrons. For the Korringa constant of ¹⁰⁹Ag we obtained κ = (10.0± 0.3) sK. Unpolarized neutrons were also used to measure the critical value of entropy S for nuclear antiferromagnetic ordering and to determine the induced magnetization M in the ordered state. The nuclear susceptibility X = μ ₀ M/B = 0.36 ± 0.01 was found to be constant, independent of S and B (B _c ≈ 100 μT).     

Muon Knight shift in palladium

The Knight shift at positive muons implanted in pure palladium has been measured as a function of temperature from 19.8 to 883 K. The Knight shift variation is strictly proportional to the Pd magnetic susceptibility with ΔK^μ/Δ_x=-(0.43±0.02) mole/emu=-(2.39±0.11)kG/μ_B. A temperature independent term K^μ(x=0)=+45±10 ppm is found. The results are discussed in terms of the electronic structure of H in Pd.     

The ferromagnetic monolayer Fe(110) on W(110)

Ferromagnetic order in the pseudomorphic monolayer Fe(110) on W(110) was analyzed experimentally using Conversion Electron Mössbauer Spectroscopy (CEMS) and Torsion Oscillation Magnetometry (TOM). The monolayer is thermodynamically stable, crystallizes to large monolayer patches at elevated temperatures and therefore forms an excellent approximation to the ideal monolayer structure. It is ferromagnetic below a Curie-temperatureT _c,mono, which is given by (282±3) K for the Ag-coated layer, (290±10) K for coating by Cu, Ag or Au and ≈210 K for the free monolayer. For the Ag-coated monolayer, ground state hyperfine fieldB _hf (0)=(11.9±0.3) T and magnetic moment per atom μ=2.53 μ_B could be determined, in fair agreement with theoretical predictions. Unusual properties of the phase transition are detected by the combination of both experimental techniques. Strong magnetic anisotropies, which are essential for ferromagnetic order, are determined by CEMS.     

Magnetic structures and magnetic susceptibilities of terbium oxysulfide and oxyselenide

For the two isomorphous compounds Tb₂O₂S and Tb₂O₂Se, the magnetic susceptibility measurements on powder samples show an antiferromagnetic ordering with Néel temperatures of about 7.7 and 7K respectively. Differing in this respect from the other rare earth oxyselenides, the magnetic anisotropy of Tb₂O₂Se at low temperature is weaker than that of Tb₂O₂S.We also determine the magnetic structures of these two compounds by neutron diffraction experiments at 1.5K. The magnetic cell is orthohexagonal and doubled along the c-axis; the magnetic moments make an angle, with the c-axis, of 47 ± 10° for Tb₂O₂S and 30 ± 10° for Tb₂O₂Se and the moment values at 1.5K are 8.14 ± 0.2μ_B and 6.5 ± 0.2μ_B, respectively.It is rather exceptional that in a rare earth uniaxial compound the magnetic moment makes an angle with the c-axis. However we interpret this situation by the fact that several levels exist very near to the ground state. The crystal field calculations are in good agreement with the experimental results.     

On the interpretation of NMR experiments in CoGa alloys

We show that in Co_xGa_1?x alloys NMR data reported by Grover et al. in combination with existing magnetization data can be interpreted as follows. The group of atoms consisting of a Co antistructure atom and its eight nearest neighbours behaves as a magnetic entity. The (saturation) magnetic moment of the anti-structure atom (?1.6μ_B) is much larger than the corresponding moment on a neighbouring Co atom (?0.16 μ_B).     

The change in the character of phase transition with nickel in the Ho(Co,Ni)2 compounds

The series Ho(Co_1-cN_c)₂ has been investigated in the composition range c?0.15 by spin-echo NMR of ¹⁶⁵Ho and by magnetic measurements. From NMR data a value of (9.5±0.1)μ_B is estimated for holmium in HoCo₂. Magnetisation measurements on the same compound give (7.9±0.1)μ_B/fu. An assumption of 0.8μ_B for the cobalt moment aligned antiparallel to that of holmium leads to a value of 9.5μ_B for holmium in agreement with the value estimated from NMR. The substitution of nickel for cobalt causes a rapid fall in both the hyperfine field, and the ordering temperatures, while the molecular moment shows a simultaneous rise. These are attributed to a rapid fall in the cobalt moment which leads to a bootstrap process involving the strength of the exchange field and the magnitude of the cobalt moment. Nickel substitution also leads to a change in the character of the magnetic phase transition. Initially first order, this transition becomes second order on exceeding ≈ 9 at% Ni.     

Neutron diffraction study of the magnetic ordering in EuAs3

The magnetic structure of one of the two ordered phases has been determined at 5 K. The magnetic structure is found to be antiferromagnetic with a cell doubling in the c direction of the monoclinic nuclear cell. The centering in the nuclear cell is replaced by anticentering. The collinear magnetic moments are parallel to the b axis. The magnetic moment per Eu atom has been found to be 5.74(6)μ_B which leads to the saturation magnetic moment of 6.5μ_B.     

Magnetic properties of xCoO.(1−x)[2B2O3.PbO] glasses

The results of magnetic studies on xCoO.(1?x)[2B₂O₃.PbO] glasses with 0?x?50 mol.%, are reported. These results show evidence that the cobalt ions, in this glass system, are in bivalent state and magnetically isolated, having magnetic moments μ=(4.50±0.06)μ_B.     

Microwave determination of the conformation and dipole moment of 1,3-difluoroacetone

The microwave spectra of the ground state and several low-lying vibrational modes of 1,3-difluoroacetone have been assigned and analyzed. The assigned form has a molecular conformation in which one fluorine atom lies cis and the other trans to the oxygen atom. The rotational constants of the ground state species were determined using a centrifugal distortion analysis: A = 6024.843 ± 0.006 MHz, B = 2454.414 ± 0.001 MHz, C = 1783.897 ± 0.001 MHz. The molecular dipole moment components of the ground state species lie along the a and b principal axes with μ_a = 2.38 ± 0.03 D, μ_b = 0.89 ± 0.03 D, and μ_T = 2.54 ± 0.03 D. Comparative intensity measurements with OCS microwave lines indicate that the assigned form constitutes only 20% to 30% of the total gas mixture, the remainder presumably consisting of one or more other conformers, perhaps the gauche-gauche form. The lowest vibrational frequency (82 ± 12 cm^?1) is attributed to the trans-CH₂F torsion, while the next-higher vibrational frequency (127 ± 15 cm^?1) is believed to be the cis-torsion. A low-frequency in-plane bending motion is found at 285 ± 25 cm^?1.     

Optical investigation of DyFeO3

Optical absorption spectra of DyFeO₃ have been investigated at 1.2≦T≦4.2 °K, andT=77 °K From the temperature dependent lineshift a Néel temperature ofT _N=(3.8±0.5) °K is deduced for the dysprosium sublattices. The groundstate splitting due to the iron-dysprosium interactions is about 1.5 cm^?1 and due to the dysprosiumdysprosium interactions (5.0±1.4) cm^?1. Zeeman studies give the magnetic moment of the dysprosium ions asμ=(9.2±1.0)μ _B.     

239PuN powder neutron diffraction study

A powder neutron diffraction study has been carried out on ²³⁹PuN, which was reported to be antiferromagnetic below T = 13 K. No magnetic ordering has been detected at 4K, the limit of the magnetic ordering which could be detected being μ_ord = 0.25μ_B per Pu atom. Moreover a neutron scattering length determination of ²³⁹Pu was performed which gave a value of b_²³⁹Pu = (0.81 ± 0.05) × 10^-12 cm at neutron wavelength $\text{λ = 1.219}\text{A}\text{?}$.     

On the origin of ferromagnetism in semiconducting TiO2−δ:Co oxide

In Co-doped TiO_2?δ oxide films deposited on SrTiO₃(100) substrates, a room-temperature ferromagnetism is found to occur only in a limited charge-carrier concentration interval from 2×10¹⁸? 5×10²² cm^?3. This indirectly testifies that ferromagnetism in the aforementioned n-type semiconductor is associated with the exchange interaction of magnetic ions via conduction electrons rather than with the formation of Co clusters in the material. The magnetic moment per Co atom is 0.8μ_B in the TiO cubic phase and 0.5μ_B in the anatase tetragonal phase of TiO₂.