Haim Pinto

Magnetic phase diagram of the U(Co1−xCux)2Ge2 system

Abstract Polycrystalline U(Co 1− x Cu x ) 2 Ge 2 solid solutions, investigated by neutron diffraction, exhibit ThCr 2 Si 2 -type crystallog raphic structure and magnetic ordering of the uranium sublattice, with moments along the tetragonal axis: antiferromagnetic [ k = (0, 0, 1)] for x = 0, 0.25 and 0.5, and ferromagnetic for x = 0.75 and 1. The tentative magnetic phase diagram (temperature versus composition) of the U(Co 1− x Cu x ) 2 Ge 2 system is proposed.

Neutron diffraction study of Ce2O3

Abstract A powder sample of Ce 2 O 3 was investigated by neutron diffraction and magnetic susceptibility measurements. The position parameters were determined and found to be similar to those in the isostructural La 2 O 3 . The effective magnetic moment was found to be 2.17 μ B /molec. No evidence was found for the existence of a magnetic or structural phase transition in connection with a specific heat anomaly previously found at 8.5 K.

Magnetic structure of PrCo2Ge2, a neutron diffraction study

The crystallographic structure of the compound PrCo2Ge2 is of the BaAl4 type. The space group is I4/mmm and the lattice constants are a = 4.048 and c = 10.178 A. A neutron diffraction study revealed a transition to a magnetically ordered state at TN ~ 27 K and six superlattice lines below TN. It is possible to index these lines according to a sinusoidal magnetic structure with a period τ-1 = 13.94 A along c. Observed intensities are consistent with ordering of the Pr sublattice with the magnetic axis along c.

Long wavelength neutron diffraction study of the magnetic structures of PrFeO3 and NdFeO3

The use of long wavelength neutrons in the study of magnetic structures in rare earth orthoferrites is discussed and demonstrated with PrFeO3 and NdFeO3. It is found that the reorientation of the Fe3+ ion in NdFeO3 (Gx → Gz) begins at 160°K and ends at 70°K.

Magnetic ordering in U(M,M’)2Ge2 compounds (M,M’=Co,Ni,Cu)

Several U(M,M’)2Ge2 compounds (M,M’=Co,Ni,Cu) have been studied by neutron diffraction. U(Co1−xCux)2Ge2 and UNiCuGe2 exhibit ThCr2Si2‐type tetragonal structure, with a=4.02–4.10 A and c=9.86–10.25 A, and a magnetically ordered uranium sublattice with moments along c. The ordering is antiferromagnetic with a wave vector k=(0,0,1) for x=0,0.25, and 0.50 and UNiCuGe2 (TN=175, 130, 100, and 140 K, respectively), and ferromagnetic for x=0.75 (TC=102 K) and 1 (TC=107 K). In UCoNiGe2 (a=4.07 A, c=9.52 A) no magnetic ordering has been found down to 10 K. Two other samples of UCo2Ge2 (a=4.04 A, c=9.44 and 9.38 A) were previously reported not to order magnetically down to 4.2 K. The absence of magnetic ordering is related to smaller c parameters and lower crystal symmetry.

MAGNETIC PROPERTIES OF TBCO3B2 STUDIED BY NEUTRON DIFFRACTION, MAGNETIZATION, AND AC-SUSCEPTIBILITY MEASUREMENTS

Neutron-diffraction measurements on TbCo3B2, with the isotope 11B, show ferromagnetic structure below 35(2) K. Ordered magnetic moments of Tb and Co were found to be in the basal planes directed parallel to each other. The Tb ordered moment is significantly smaller than its free-ion value. The Co ordered moment is nearly zero. Ac-susceptibility and SQUID magnetometer measurements agree with the neutron results.

Neutron diffraction study of the magnetic structure of the intermetallic compound DyRh2Si2

A study of the magnetic structure of the intermetallic compound DyRh2Si2 (I4/mmm) was performed using neutron (2.459 A) diffraction of a powder sample. Below 52 K the diffraction patterns reveal a type I antiferromagnetic structure on the Dy sublattice, with a magnetic moment of 9.9±1 μB per ion along c. The appearance of a weak 001 reflection below 18 K is interpreted as due to canting (∼19 °) of the Dy moment from the c axis.

Is Fe2TiO5 an anisotropic spin glass

Abstract It is argued that the undiluted insulating oxide Fe 2 TiO 5 freezes into an anisotropic spin state below T = 55 K, such that the Fe 3+ spins are randomly aligned along the crystallographic c axis. This conclusion is supported by susceptibility, neutron scattering, ultrasonic, specific heat, and oriented single crystal Mossbauer data.

Local atomic volume dependence of Tb and Co magnetic moments

The individual sizes and orientations of the magnetic moments of Tb and Co in different sites were studied by neutron diffraction of Tbn+1Co3n+5B2n (n=1, 2, 3, and ∞). Total magnetic moments obtained by our neutron diffraction measurements are in agreement with the literature and our superconducting quantum interference device measurements. The local atomic volumes dependence of Tb and Co magnetic moments are discussed using the Wigner–Seitz cell construction method.

Magnetic phase diagram of the U(Ni1−xCux)2Ge2 system

Abstract Polycrystalline U(Ni 1- x Cu x ) 2 Ge 2 solid solutions, investigated by neutron diffraction and AC susceptibility, exhibit the ThCr 2 Si 2 -type crystal structure and magnetic ordering of the uranium sublattice, with moments along the tetragonal axis: antiferromagnetic type-I (AF-I) [ k =(0,0,1)] for x =0,0.25, and 0.50; ferromagnetic below T c , becoming at T 0 ( T c ); AF-I for x =0.75 and ferrimagnetic [ k =(0, 0, 2/3)] for x =0.90; and ferromagnetic for x =1. The tentative magnetic phase diagram ( T versus x ) of the U(Ni 1- x Cu x ) 2 Ge 2 system is proposed.