Mn Single Crystals Research Articles

Ferromagnetic phenomenon revealed in the chalcopyrite semiconductor CdGeP2:Mn

High concentration of Mn atoms has been successfully incorporated into the chalcopyrite type II–IV–V2 semiconductor CdGeP2 by solid-state reaction technique without causing any structural changes. Polycrystalline powder of the chalcopyrite-related material in Cd–Mn–Ge–P quaternary system has been additionally synthesized by sintering technology. Well-defined M–H hysteresis loops were observed at room temperature in CdGeP2:Mn single crystal and polycrystalline powder samples grown independently. The Curie temperature has been determined to be 320 K for single crystal phase CdxMn1−xGeP2 and 310 K for the polycrystalline powder. Magnetic force microscopy (MFM) observation clearly showed a stripe domain pattern on the Mn-diffused surface of CdGeP2 single crystal. The magneto-optical Kerr ellipticity spectrum of CdGeP2:Mn crystal showed a peak around 1.75 eV at T=300 K.

Recrystallisation textures of particle-containing Al–Cu and Al–Mn single crystals

The influence of second-phase particles on the recrystallisation textures of rolled Al–Cu and Al–Mn single crystals is studied. Single crystals with the initial orientations (011)[100], (011)[21 1 ̄ ] , (112)[11 1 ̄ ] and (001)[100] are investigated by means of X-ray pole figure measurements and TEM microstructure analysis. The recrystallisation textures are interpreted in terms of a growth selection out of a limited spectrum of nucleus orientations. In the case of stable initial orientations the nucleus spectrum is produced by the lattice rotations within the deformation zones around the second-phase particles. For unstable orientations the nucleus spectrum can be attributed to the rotation paths during the orientation changes upon rolling deformation (orientation splitting or rotations). During the subsequent growth selection, orientations with a 40°〈111〉 orientation relation to the rolling texture prevail and, thus, form the recrystallisation textures observed. Interestingly, this preference of grains with a 40°〈111〉 orientation relation occurs at the very early phases of recrystallisation, right at the transition from a potential nucleus to a recrystallised grain. This process is labelled micro-growth selection.

DC Electroluminescence from ZnS:Mn Crystals

The dc electroluminescence from ZnS and ZnS:Mn single crystals was studied at room temperature. The effect of annealing in the Zn melt or saturated Zn vapor on the electrical conductivity and electroluminescence of ZnS crystals was shown to be related to the field-enhanced thermal ionization of impurities.

Hot Deformation Microstructures of Al-1%Mn Single Crystals

To determine the basic mechanisms of substructure development within the grains of hot rolled Al alloys, the influence of processing conditions on the hot channel-die compression structures of Al-1%Mn single crystals has been systematically characterised by automatic EBSD orientation maps. Analysis of the microstructures gives the subgrain sizes and misorientation angle distributions, which can be described by physically based mathematical functions. The average subgrain size decreases, as expected, with increasing Zener-Hollomon parameter Z (or increasing flow stress). Most crystals have similar subgrain sizes and distributions. In contrast, the Cube oriented crystals are composed of bands of fine and coarse subgrains. The average adjacent disorientation are also quite similar and are shown to increase with flow stress (or Z). However, the spatially heterogeneous structures of the cube grains are associated with significantly higher average disorientations.

Excitation spectra and structure of luminescence centers of manganese ions in single crystals of zinc sulfide

We investigate the photoluminescence excitation spectra in ZnS:Mn single crystals at room temperature and at the temperature of liquid nitrogen with a different concentration of Mn2+ ions. The strongest bands peaking at 557, 578, 600, and 637 nm are associated with a different position of the Mn ion in the lattice of the crystals under investigation. The difference obtained in the excitation spectra can be explained by the resonance transfer of energy between the Mn ions.

Lattice disorder induced by nitrogen-ion implantation in single crystal MnZn ferrite

Abstract Single crystal MnZn ferrite was implanted with nitrogen molecule ions (N + 2 ) at 100 keV to investigate the annealing behavior of the implantation-induced damage at temperatures of 400–900°C. The lattice disorder was investigated by Rutherford backscattering combined with ion channeling. The annealing behavior of the lattice disorder revealed that two kinds of lattice distortion exist in the implanted crystal; the distortion that exists at a depth greater than the projected range was recovered by annealing at 700°C, whereas the distortion at the shallower depth was not recovered completely by annealing at 900°C. A discussion on the nature of the two kinds of lattice distortion is presented.

Epitaxial growth of Mn 3O 4 film on MgO(0 0 1) substrate by plasma-assisted molecular beam epitaxy (MBE)

Single-crystal Mn 3O 4 thin film with distorted spinel structure had been grown on MgO(0 0 1) substrate by plasma-assisted molecular beam epitaxy (MBE). It is found that single-crystal spinel Mn 3O 4 film can only be fabricated at certain growth conditions, otherwise, other phases of Mn oxides will be obtained. The surface of single-crystal films shows perfect crystallized pyramided hillocks consisting of facets {1 0 15}, and its [1 1 0] and [0 0 1] axes are separately parallel to the [1 0 0] and [0 0 1] axes of MgO(0 0 1) substrate. The quality of the Mn 3O 4 epitaxy films closely depends on the quality of the substrate. For thicker films (near 1 μm), the full-width at half-maximum of the Mn 3O 4(0 0 4) peak reaches its minimum value 0.17°.

Atomic and magnetic correlations in a Cu–5 at% Mn spin-glass alloy

Measurements of atomic and magnetic correlations in the plane perpendicular to the [1, 0, 0] axis for a Cu–5 at% Mn single crystal at low temperatures using polarised neutrons give clear evidence of weak atomic short-range correlations represented by broad humps close to (1, 1 2 , 0) -type positions while magnetic correlations are evidenced as strong low Q-scattering and SDW-like peaks at (1, 1 2 ±δ, 0) -type positions, as well as humps centred on (1, 1 2 , 0) positions. The latter are superposed on a quasi-uniform ‘background’ of magnetic scattering representing a large fraction of the spin system frozen into quasi-random orientations at low temperatures. We suggest that the periodic nature of the lattice and the relatively strong magnitudes of the antiferromagnetic first-neighbour and ferromagnetic second- and third-neighbour interactions give rise to the SDW-like short-range order while the effect of the small amount of atomic short-range order is to enhance the latter at the expense of the uniform cross-section representing the randomly frozen spin system.

Nuclear magnetic relaxation studies of 69Ga, 71Ga, and 75As nuclei in GaAs single crystals doped with paramagnetic impurities

The GaAs, GaAs:In,Cr, and GaAs:Mn single crystals were grown by the vertical gradient freeze (VGF) technique. The spin-lattice relaxation processes of 69Ga, 71Ga and 75As have been studied for the undoped GaAs single crystals and crystals doped with paramagnetic impurities Cr and Mn. The relaxation processes in all samples are well described by a single exponential function. The T 2 dependence of the relaxation rate was in accordance with that predicted for the Raman mechanism of nuclear spin-lattice relaxation for all crystals investigated. The manganese doping showed a tendency to shorten slightly the spin-lattice relaxation times.

Magnetostriction of TbyDy1-y(Fe1-xTx)2(T=Al,Mn) and Their Intrinsic Magnetostrictive Properties

Magnetostriction of TbyDy1-x(Fe1-xTx)2(T=Al,Mn) single crystals, prepared by the MCGS-3 CZ instrument, was investigated. The intrinsic magnetostrictive properties were derived by fitting method of X-ray diffraction patterns of polycrystal samples prepared by arc-melting method. The substitution of AL, Mn for Fe lowers the saturation field and magnetocrystalline anisotropic energy. The intrinsic magnetostriction, 111, decreases with increasing amount of Al or Mn. For Tb0.5Dy0.5(Fe0.9Mn0.1)2 single crystals,a large magnetostriction and high d33 can be obtained under the compressive stress of 1226 MPa.

Conductivity and NMR Study of LaGa1−xMnxO3 Single Crystals

AbstractElectrical conductivity and magnetic relaxation has been studied in single crystals of Mn doped LaGaO3 with doping concentrations of 0%, 0.5%, 2%, 10% and 50%. The resistivity of the crystals strongly depends on temperature and can be described with the hopping model. Both activation energy and resistivity coefficient grow significantly with decrease in Mn ion concentrations. Dramatic changes are observed in 71Ga NMR spin-lattice relaxation times.

Macroscopic and microscopic subdivison of a cold–rolled aluminium single crystal of cubic orientation

An aluminium single crystal of cube orientation has been rolled to 15, 30 and 50% reductions under controlled homogeneous rolling conditions. The deformation structure of the rolled specimens was investigated by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) over several scales of magnification. The local crystallographic orientations have been measured by an automatic electron back scattering patterns (EBSP) technique and a semiautomatic TEM method. Orientation image maps based on the local orientation data have been used to reveal the evolution of the deformation structure during rolling. It is observed that by an opposite rotation around transverse direction (TD) the crystal was subdivided into four macroscopic bands, termed matrix bands in the present paper, which are parallel to the rolling plane. Between the four bands there are three transition bands in which the orientation changes continuously from that of a matrix band to that of the adjoining one. A model based on the idea of location–dependent shear strain caused by geometric and friction effects together with a plasticity analysis has been used to explain the macroscopic subdivision of the crystal. In addition to the macroscopic subdivision, a microscopic subdivision by the formation of cell–blocks within the matrix bands and a cell structure within transition bands has also been observed. A difference related to shear amplitude difference between the active slip systems changing continuously across the crystal has been observed. Both the macroscopic orientation of the dislocation boundaries and the misorientation angles and axes across dislocation boundaries are analysed and it is found that Frank9s formula is a useful tool in analysing the dislocation boundaries formed during deformation.

Magnetic small-angle scattering from Cu-17 at.% Mn

Two Cu-17 at.% Mn single crystals quenched to room temperature after aging at 483 and 553 K, respectively, were investigated by small-angle neutron scattering between room temperature and 15 K. While nuclear small-angle scattering is low and increases only slightly towards the direct beam, strong magnetic small-angle scattering is observed. Its intensity increases with increasing degree of chemical short-range order and decreasing temperature. The correlation lengths for chemical and (static) ferromagnetic fluctuations are comparable.

The nature of manganese luminescence centers in zinc sulfide single crystals

This paper discusses how the luminescence-excitation method affects the spectral content of the emission in ZnS: Mn single crystals. It shows that the nearest neighborhood of the Mn2+ ions is associated with the elementary emission bands having maxima at the wavelengths λm=557, 578, 600, 616, and 638±2 nm in zinc sulfide crystals with different manganese concentrations.

Crystal growth and structure of Mn 2.47V 0.94Mo 1.06O 8

Single crystals of Mn 2.47V 0.94Mo 1.06O 8 were grown in a MnO/V 2O 5/MoO 3 melt under a nitrogen atmosphere (orthorhombic, space group Pnma (No. 62), a=5.167(2) Å, b=10.580(3) Å, c=17.868(4) Å, and Z=6). The crystallization, composition, and quality of the crystals were largely influenced by the composition of the melt, temperature and the oxygen partial pressure.

Spin–wave instability measurements in Mn substituted single-crystal Zn2Y hexagonal ferrite thin disks at 8.9 GHz (abstract)

Large magnetocrystalline anisotropy makes hexagonal ferrites attractive for microwave and millimeter wave applications. Critical to such applications is the response at high power levels. Relatively little work has been reported in this area. In order to characterize this response, the minimum microwave field amplitude required to excite spin–wave instability, hcrit, is measured for various field–sample configurations. Plots of hcrit versus static field H, termed “butterfly” curves, are then used to obtain spin wave linewidths and define operational power limits for device applications. Two regimes were studied in this work: (1) saturation of the ferromagnetic resonance (FMR) absorption; and (2) parallel pumping instability for fields well below FMR. The objective was to measure butterfly curves and use the results to determine values of the spin–wave linewidth ΔHk. The measurements were made on a 1.2 mm diam 0.15 mm thick single-crystal Mn substituted Zn2Y (Y-type) hexagonal ferrite c-plane (001) disk with easy plane anisotropy. The static field and the 4 μs wide, 30 Hz pulsed microwave field at 8.9 GHz were applied in the plane of the disk. Standard cavity techniques were used. The low power ferromagnetic resonance (FMR) linewidth was 15 Oe. For resonance saturation, the measured hcrit was 0.29 Oe at the FMR field of 775 Oe. The resonance saturation butterfly curve was asymmetric about its minimum value at FMR. The hcrit for parallel pumping was approximately 5 Oe and independent of H over the range of 150–350 Oe. These data and spin–wave instability theory were used to estimate ΔHk values. For parallel pumping, ΔHk was determined to be 17 Oe for the critical modes at one half the 8.9 GHz pump frequency. For resonant saturation, ΔHk was determined to be 12 Oe for the critical modes at the pump frequency.

Low-Temperature Neutron and X-Ray Diffraction Studies on Mn(cth)Cu(oxpn)(CF3SO3)2: (cth) = (+-)-5,7,7,12,14,14-Hexamethyl-1,4,8,11-tetraazacyclotetradecane; (oxpn) = N,N'-Bis(3-aminopropyl)oxamide.

The present investigation shows the complementarity of neutron and X-ray diffraction studies. Neutron and X-ray diffraction experiments on a single crystal of Mn(cth)Cu(oxpn) (CF3SO3)(2) have been performed in order to study the nuclear structure and to

Microtribological studies of Al 2O 3, Al 2O 3TiC, polycrystalline and single-crystal MnZn ferrite, and SiC head slider materials

Surface topography, friction, scratching, wear and nanoindentation behavior of head slider materials were studied using atomic force/ friction force microscopy (AFM/FFM). Materials studied include polycrystalline Al 2O 3, Al 2O 3TiC (70-30 wt.%), polycrystalline MnZn ferrite, single-crystal MnZn ferrite and polycrystalline SiC. Al 2O 3 is not used for construction of head slider but it was studied for comparisons with Al 2O 3TiC. SiC is a candidate slider material. The Al 2O 3TiC specimen exhibits the highest coefficient of microscale friction followed by polycrystalline MnZn ferrite, Al 2O 3, single-crystal Mn ferrite, Al 2O 3, single-crystal MnZn ferrite and SiC. Two phase Al 2O 3TiC exhibited higher microscale friction than a single phase Al 2O 3 and polycrystalline MnZn ferrite exhibits microscale friction than a single-crystal MnZn ferrite. The local variation in friction force for Al 2O 3, polycrystalline and single-crystal MnZn ferrite was found to correspond to the lcoal surface slope (first derivative of the surface roughness profile). For Al 2O 3TiC and SiC specimen, the local variation in friction force at the scratches corresponds to the local surface slope. However, local variation over entire region corresponds to the different phases present on the specimen surface. Thus friction force imaging can be used for structural mapping of the surfaces. Directionality effects in the friction were studied on a microscale for the Al 2O 3 specimen. Macroscale friction values for all samples are higher than microscale friction values as there is less ploughing contribution in microscale friction measurements. Microscratching/wear studies indicate that scratch and wear resistance of SiC and Al 2O 3 are higher than that of the other specimens. However, Al 2O 3 specimen shows the presence of porous holes on the surface that affect the wear performance. Al 2O 3 specimen exhibits superior microscratch and microwear resistance than Al 2O 3TiC. Wear evolution for single and two phase materials was studied in detail. Nonoindentation hardness values found to be generally higher than that of microhardness data. Based on these measurements, coefficient of friction, microscratch and microwear resistance of singe phase materials are superior to that of two phase materials.

Atomic and magnetic short-range order in Cu-17 at.% Mn

In noble-metal alloys, diffuse peaks have often been observed at 1 1/2 {+-} {delta} 0 positions in diffuse neutron or X-ray scattering experiments. These peaks are connected with the presence of flat regions of the Fermi surface and are called 2k{sub F} peaks. They were found in the magnetic scattering of {und Cu}-Mn and {und Ag}-Mn as well as in the chemical, i.e. non-magnetic scattering of {und Cu}-Al, {und Cu}-Zn, {und Cu}-Pd, {und Ag}-Mn and {und Au}-Mn. The aim of the present study was to investigate the diffuse magnetic and chemical scattering of a Cu-17.2 at.% Mn single crystal. Although 2k{sub F} peaks are expected in the chemical scattering of {und Cu}-Mn as well, they were not found in earlier neutron scattering studies.

Photoluminescence of Ga 2S 3 and Ga 2S 3: Mn single crystals

Photoluminescence spectra of Ga 2S 3 and Ga 2S 3 : Mn single crystals prepared by the chemical transport reaction method were investigated. We observed a relatively narrow band at 2.14 eV (514 nm) and a broad band centered at 1.81 eV (685 nm) for Ga 2S 3 at 10 K. For Ga 2S 3 : Mn, on the other hand, a dominant emission band at 1.81 eV (685 nm) and three weak emission bands at 2.34 (530), 2.14 (579) and 1.54 eV (805 nm) are observed. The origins of the emission bands are identified on the basis of the energy-band scheme proposed from the measurements of optical absorption, TSC and PICTS. The results show that two emission bands for Ga 2S 3 are attributed to the electron transition from the donor level to the acceptor levels, and four emission bands for Ga 2S 3 : Mn are associated with the transitions from the excited state 4T 1( 4G) of Mn 2+ to the ground state 6A 1( 6S) and the acceptor levels.