Tomiei Hori

Magnetization and coercivity of Mn3−δGa alloys with a D022‐type structure

The D022‐type (Al3Ti‐type) phase in the Mn–Ga system is ferrimagnetic; the spin direction is parallel to the tetragonal c axis. The Curie temperature is about 765 K (for δ=0.67), near the decomposition temperature. We have prepared the D022‐type alloys by annealing the quenched ingots of the high‐temperature phase (γMn phase) at 400 or 300 °C for a long time. The preparation becomes much easier if the ingots are powdered by filing before the annealing. The single‐phase specimens of Mn3−δGa were obtained in the composition range 0.15≤δ≤1.06. The coercivity of some specimens was so large that we measured the magnetization curve in high magnetic fields up to 150 kOe. The room‐temperature values of saturation magnetization, remanent magnetization, and coercivity of the powder sample of the alloy with δ=0.67 are 50 emu/g, 25 emu/g, and 13.5 kOe, respectively. We have also studied the effect of magnetic annealing during the transition from the γMn phase to the D022‐type phase and the effect of the addition of F...

Magnetic Properties and Crystal Distortion of Hexagonal Mn3 Ga

Magnetization measurements and X-ray diffraction experiments have been made on e -Mn 3 Ga (71.4 at%Mn) having a triangular spin structure with a weak ferromagnetic component below 460 K. It has been found that the D0 19 -type hexagonal structure is slightly distorted to an orthorhombic structure below 170 K, and that the transition is accompanied by a steep increase of spontaneous magnetization. The crystal distortion may enhance the deviation from the ideal triangular spin configuration.

Magnetization and Magnetic Structure of Mn-Zn and Mn-Zn-Ga Alloys of CsCl-Type Structure

The β 1 phase of the CsCl-type structure in Mn-Zn system, which exhibits strong ferromagnetism at room temperature, was found to be stable below 175°C. Its homogeneity range extends from 50 to 56.5 at.% Mn. A canted spin structure, i. e. a coexistence of ferromagnetic and antiferromagnetic moments which are orthogonal to each other, was revealed to exist by the technique of neutron diffraction. Both moments decrease with increasing Mn content. An attempt to substitute a third element for Zn or Mn was unsuccessful except for Ga. The β 1 phase can contain as much as 10% Ga. The substitution of Ga for Zn gives rise to an increase in ferromagnetic moment and a decrease in antiferromagnetic moment.

Magnetic Structure of the Intermetallic Compound MnHg

The antiferromagetic structure of MnHg was investigated by neutron diffraction measurements on the powder sample. The Mn atoms are arranged on a simple cubic lattice, which splits into two face centred cubic sublattices so that the magnetic moments on one sublattice are antiparallel to those on the other. The magnetic moment of a Mn atom is close to 4 Bohr magnetons. The angles between the magnetic moments and the crystallographic axes remain undetermined. The Neel point is evidently higher than 300°K, and there is no remarkable change in the neutron diffraction pattern at 198°K, where the magnetic susceptibility exhibts a distinctive anomaly and the crystal lattice undergoes a slight distortion from cubic to tetragonal symmetry.

Crystal distortion and weak ferromagnetism of Mn3+δGa1−xGex alloys

The compound Mn3Ga (70–74 at.% Mn) has the hexagonal DO19‐type structure, and a triangular antiferromagnetic spin structure with a weak ferromagnetic component below the Neel temperature of about 470 K. Below 170 K the hexagonal structure is distorted to an orthorhombic one, accompanied by a steep increase in the ferromagnetic component. X‐ray‐diffraction experiments and magnetization measurements have been made for a pseudobinary system Mn3+δGa1−xGex. It was found that the DO19‐type structure is stable at 600 °C in the whole composition range 0≤x≤1.0 with appropriate values of δ. The Neel temperature of the triangular spin structure decreases with increasing x with a gentle slope. The crystal distortion temperature decreases more steeply and vanishes near x=0.6.

Imaging of Rabbit VX-2 Hepatic Cancer by Cold and Thermal Neutron Radiography

Neutron radiography is based on differences in neutron mass attenuation coefficients among the elements and is a non-destructive imaging method. To investigate biomedical applications of neutron radiography, imaging of rabbit VX-2 liver cancer was performed using thermal and cold neutron radiography with a neutron imaging plate. Hepatic vessels and VX-2 tumor were clearly observed by neutron radiography, especially by cold neutron imaging. The image contrast of this modality was better than that of absorption-contrast X-ray radiography.

Magnetic properties of Ni2In type (Co1–xMnx)65Ge35 compounds

The high temperature phase of (Co1–x Mn x ) 65Ge35 is found to be of the hexagonal Ni2In type in the range of 0≤x≤0.6. Co2Ge is Pauli paramagnetic, and ferromagnetism is induced with substitution of Mn for Co. Magnetization measurement and x‐ray diffraction experiments for these compounds have been performed. The x dependences of the Curie temperatureT c and magnetization show a maximum near composition x=0.25. X‐ray studies show that the lattice constantsc are minimum at x=0.25. The x dependence of the relative intensities of x‐ray lines suggests that the Mn and Co atoms at 2(a) sites in the compound x=0.25 align alternately in the c direction. The Co atoms at 2(d) site and the Ge atoms at 2(c) site shift along the c direction are found. The neutron diffraction experiment of x=0.25 also support such crystal structure. Maximum of Curie temperature and magnetization of compounds near x=0.25 are discussed with the ordering of Mn and Co atoms in the crystal lattice.

Magnetic and neutron diffraction study on Ni2In type (Mn1−xPdx)2Ga

Pseudobinary intermetallic compounds (Mn1−xPdx)2Ga of Ni2In type structure are found in the range of 0.3≦x<0.6. This article describes the results of investigations of the crystal and magnetic properties of the phase with x-ray and neutron diffraction, as well as magneto metric methods. The neutron diffraction study for x=0.4 proved that in the Ni2In type crystal structure, the 2(a) site is occupied by Mn atoms, the 2(d) site by Pd and residual Mn atoms, and the 2(c) site is occupied by Ga atoms. (Mn1−xPdx)2Ga compounds exhibit a ferromagnetic nature characterized by TC, and in the temperature below TN, antiferromagnetic components originating from canted spin structure in 2(a) structures in the 2(a) site. It is similar to canted spin structures of CoMnSn. The existence of a small concave region in the magnetization–temperature dependence curve is discussed in terms of the canting of spins in the 2(a) site.

Magnetic properties of (Mn1−xFex)3+δGe alloys

Abstract We have made X-ray, magnetization and electric resistivity measurements for (Mn 1−x Fe x ) 3+δ Ge with the D0 19 -type structure, and determined the x -dependence of the Neel temperature, the Curie temperature and a transition temperature from the triangular to the collinear magnetic structure for the alloys with δ=0.1 and 0 ⩽ x ⩽0.34. An abrupt change at the transition shows a remarkable thermal hysterisis.

Magnetic Properties of C16 Type Mn1-xFexSn2 Compounds by Mössbauer Study

We have measured 57Fe Mossbauer spectra at temperature 13 K and 77 K. The Mossbauer data at 13 K are 120–160 kOe for the hyperfine field Hi, near zero for the quadrupole energy shift ΔE and 0.6 mm/s for the isomershift. Hi and ΔE at 77 K show an anomaly between x=0.8 and x=0.85, corresponding to the change of magnetic structure A.F. I\rightleftarrowsA.F. III. The composition x dependence of Hi curve shows an anomalous decrease at x=0.6. The composition dependence of Mossbauer data is discussed in the relation to the sublattice magnetization and the electronic states of Fe.