Magnetization Of Single Crystals Research Articles

A single-crystal magnetization and neutron scattering investigation of the magnetic structure of

is a member of a large family of intermetallic compounds with the tetragonal crystal structure. It orders antiferromagnetically at with the propagation vector k = (0,0,1/2). We have performed magnetization and neutron scattering experiments on a single crystal that show that the uranium atoms order in the collinear irreducible representation of the magnetic group, with the moments aligned parallel to the unique tetragonal axis. The value of the ordered magnetic moment of the uranium atoms refined from the neutron scattering intensities is . This is considerably reduced from the free-ion value for both and configurations and suggests that the f electrons are strongly hybridized with the conduction band.

Anisotropic magnetoresistance of single-crystal HoNi2B2C and the interplay of magnetic and superconducting order.

The in-plane resistivity and magnetization measurements as a function of the magnitude and direction of the magnetic field and the temperature are reported for single-crystal samples of the Ho${\mathrm{Ni}}_{2}$${\mathrm{B}}_{2}$C magnetic superconductor. Features corresponding to several distinct magnetic phases and the coexistence of superconductivity with two of the magnetic phases are observed. Contrary to previous measurements for polycrystalline samples, reentrant superconductivity is not observed in the absence of a field for these samples. The measurements indicate an extremely rich interplay between superconductivity and different magnetic structures that can be influenced by field, temperature, and current. The results correlate quantitatively with and complement previous determinations of the magnetic phase diagram and qualitatively with determinations of the superconducting phases by measurements of the single-crystal magnetization and heat capacity. Ho${\mathrm{Ni}}_{2}$${\mathrm{B}}_{2}$C is highly anisotropic, and phase diagrams for the field along the (100) and (001) directions are presented.

Crystal structure and magnetic properties of the layer ferrimagnet N(n-C5H11)4MnIIFeIII(C2O4)3

The crystal structure and magnetic properties of the molecular-based ferrimagnet N(n-C5H11)4MnIIFeIII(C2O4)3 have been determined. The compound is orthorhombic, space group C2221, a= 9.707(3), b= 16.140(3), c= 19.883(7)A(120 K), Z= 4[R 0.047 for I > 2σ(I)]. The structure consists of hexagonal layers of alternating MnII and FeIII bridged by C2O42–, separated by layers containing only N(n-C5H11)4+ with the alkyl chains extended, though with the terminal bonds twisted towards the gauche conformation. The terminal CH3 are embedded in the hexagonal pockets formed by three C2O42–. Since both metal ions have 3d5 configuration with 6A1 ground states the magnetic properties in the paramagnetic region mimic those of a two-dimensional antiferromagnet. Below TN= 27 K an uncompensated moment estimated as 8.78 × 10–5µB atom–1 arises, the direction of which was identified as parallel to the c axis by single-crystal magnetization measurements.

Nonlinear Meissner effect in unconventional superconductors.

We examine the long-wavelength current response in anisotropic superconductors and show how the field-dependence of the Meissner penetration length can be used to detect the structure of the order parameter. Nodes in the excitation gap lead to a nonlinear current-velocity constitutive equation at low temperatures which is distinct for each symmetry class of the order parameter. The effective Meissner penetration length is linear in $H$ and exhibits a characteristic anisotropy for fields in the $ab$-plane that is determined by the positions of the nodes in momentum space. The nonlinear current-velocity relation also leads to an intrinsic magnetic torque for in-plane fields that are not parallel to a nodal or antinodal direction. The torque scales as $H^3$ for $T\rightarrow 0$ and has a characteristic angular dependence. We analyze the effects of thermal excitations, impurity scattering and geometry on the current response of a $d_{x^2-y^2}$ superconductor, and discuss our results in light of recent measurements of the low-temperature penetration length and in-plane magnetization of single-crystals of $YBa_2Cu_3O_{7-\delta}$ and $LuBa_2Cu_3O_{7-\delta}$.

Magnetisation measurements in U14Au51

Single-crystal magnetisation measurements are reported for the intermetallic compound U14Au51-. Two magnetic phase transitions are identified at low temperatures. The results are compared with measurements carried out on powder samples.

Magnetic structures of the Mn III weak ferromagnets AMnF4.H2O (A=Rb and K)

Neutron diffraction experiments on powder samples and single-crystal magnetization measurements are used to determine the magnetic structure of KMnF4.H2O and RbMnF4.H2O. Both compounds order as antiferromagnets in the magnetic space group C2'/c' ar, respectively, 8.3 K and 8.5 K. Their respective magnetic moments are located in the ac plane and deviates from strict antiparallelism by about 1.5 degrees .

Formation of multi-polar crystalline and magnetic grain orientation for manufacturing one-piece rotor magnets from Nd-Fe-B alloy and monocrystalline Fe-Co-Cr

The authors discuss the problems related to the formation of the orienting magnetic field during compaction of Nd-Fe-B powder and thermomagnetic treatment of Fe-Co-Cr single-crystal magnets. The orientation of the magnetization vector that provides maximum magnetic flux has been calculated for quadripolar magnets as an example. Ways to obtain optimum orientation have been found. It has been shown that the application of one-piece multipolar magnets makes it possible to increase magnetic induction in the operational gap by 20-40%.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A study of crystal fields in Yb 2Fe 14B by 174Yb Mössbauer spectroscopy

The compound Yb 2Fe 14B has been investigated by Mössbauer spectroscopy with 174Yb in the temperature range 4–125 K. Values of crystal field parameters and Yb-Fe exchange energies have been derived from a simultaneous fit to 5 spectra. The results are compared with those derived from single-crystal magnetization data for isostructural compounds with other rare earth ions.

Magnetic structure and magnetic properties of the spinel solid solutions ZnCr2xAl2-2xS4(0.85⩽x⩽1). II. Magnetic properties

For pt.I see ibid., vol.19, p.1783 (1986). The spinel solid solutions ZnCr2xAl2-2xS4 (0.85<or=x<or=1) have been studied by means of Mossbauer spectroscopy and magnetisation measurements. For the pure compound, several samples (powders and single crystal) have been studied. The existence of the three magnetic phases, determined by neutron diffraction (part I of this study), has been conformed by Mossbauer spectroscopy and the values of the hyperfine parameters are given. The variation of these parameters with temperature shows that the magnetic phase transition at T0 is of first order. No irreversibilities and quasi-isotropical properties are established for the single-crystal magnetisation, due to the existence of the three phases. No true difference occurs when the chromium is diluted by aluminium, in the dilution range studied.

Sintered single-crystal magnets of alloys based on the system Fe-Ni-Al-Co

Sintered single-crystal magnets of alloys based on the system Fe-Ni-Al-Co

Magnetic properties of NdAl2

The magnetic properties of NdAl2 are calculated using a Hamiltonian including crystal-field and isotropic exchange interaction terms. A two-dimensional mean-field theory is evaluated to calculate single-crystal magnetization curves. It is shown that the magnetic properties can be understood using the crystal-field parameters derived from the magnetic exciton spectrum measured by Houmann et al. by means of inelastic neutron scattering. The combined lambda -Schottky anomaly in the heat capacity is explained. No additional parameters are introduced.

Magnetic Hysteresis of Holmium Metal at 4.2°K

Hysteresis loops are presented for a specimen of polycrystalline holmium metal at a temperature 4.2°K. The curves differ significantly from those previously reported, but such differences are not unexpected between two different samples of polycrystalline metal. Most qualitative features of the curves follow simply from single-crystal magnetization curves if a random distribution of c axes is assumed. The unusual position of the initial magnetization curve outside the hysteresis loops can be explained by a condition of zero-field stability for both a ferromagnetic and an antiferromagnetic structure.

Single-Crystal Magnetization Data for Anisotropic Rare-Earth Iron Garnets at Low Temperatures

Single-crystal magnetization measurements using a force method and fields up to 17 000 Oe applied in the principal crystal directions are presented for TbIG, DyIG, HoIG, ErIG, and SmIG in the range 20°–300°K. In the region below 100°K, where these garnets have high anisotropies, the results differ from the original measurements of Pauthenet on polycrystalline samples by as much as 6 μB, though the compensation temperatures found are close to those of Pauthenet. Residual anisotropies in the magnetization &amp;lt;1 μB are apparent for ErIG and TbIG below 80°K.