The ternary rare earth compound SmRh4B4 has been studied by means of upper critical field, low temperature specific heat, and static magnetic susceptibility measurements. A lambda-type specific heat anomaly, a discontinuity in the slope of the upper critical field versus temperature curve, and a cusp-like feature in the magnetic susceptibility suggest that superconductivity and long-range antiferromagnetic order coexist in SmRh4B4 below 0.87 K. Machida's theory for antiferromagnetic superconductors provides a good description of the upper critical field data, while the magnetic susceptibility data can be represented as the sum of a Curie-Weiss term with microeff = 0.632 microB and θp = -1.93 K and a temperature independent Van Vleck contribution. © 1979.

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 μeff = 3.58 ± 0.05 μB and a Curie-Weiss temperature θp = -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. © 1979.

The results of neutron-diffraction measurements are reported which confirm that superconducting TmRh4B4 orders magnetically at TM0.7 K. The modulated antiferromagnetic structure deduced from the data is of particular interest, considering the similarity of certain other physical properties of TmRh4B4 to those of the ferromagnetic, reentrant superconductor ErRh4B4. © 1983 The American Physical Society.

The results of neutron-diffraction measurements are reported which confirm the development of long-range magnetic order in superconducting NdRh4B4. Two distinct antiferromagnetic transitions occur below the superconducting phase-transition temperature TSC=5.4 K, one at TMH 1.5 K and the other at TML 1.0 K. In both phases, the body-centered tetragonal sublattice of Nd atoms orders antiferromagnetically with the Nd3+ moments aligned along the unique c axis. The magnetic moment is modulated sinusoidally along the [100] direction in the higher-temperature magnetic phase and along the [110] direction in the lower-temperature phase. The measured saturation moment is 3.4± 0.5μB. No ferromagnetic component could be detected in the higher-temperature magnetic phase within an experimental sensitivity of 0.3μB. © 1982 The American Physical Society.

We have used neutron scattering techniques to examine the magnetic transitions in the Ho1-xErxRh4B4 pseudoternary system. A wide variety of behavior is found, ranging from mean-field behavior for HoRh4B4 to complicated behavior for ErRh4B4, where superconductivity and long-range ferromagnetic order coexist between 0.7 and 1.2 K. Long-range ferromagnetic order is found at the lowest temperatures for all alloy compositions. Alloys with more than about 30% Ho order magnetically along the c axis and superconductivity is destroyed in these alloys in a sharp transition coincident with magnetic ordering. Alloys near the ErRh4B4 composition order in the basal plane but undergo a complex ordering process through a sinusoidally modulated state. Because Ho and Er have competing orthogonal magnetic anisotropies, compounds near the composition Ho 0.25Er0.75Rh4B4 are near a multicritical point in the magnetic phase diagram.

Superconductivity and magnetism are two types of order that can take place in materials at low temperatures. When the magnetic order is ferromagnetic, a competition exists between magnetism and superconductivity. Neutron scattering has been used to measure the interaction of magnetism and superconductivity in a series of ternary rare-earth alloys. A wide range of behavior is found near the magnetic transition, including mean-field magnetic ordering, first-order transitions between magnetism and superconductivity, and co-existence of ferromagnetism and superconductivity with a sinusoidally-modulated magnetic phase. © 1983.

A new family of rare earth-rhodium-tin intermetallic compounds, with the representative formula (RE)RhxSny, has been synthesized in single crystal form. The compounds containing the heavier rare earths are superconducting and those with the lighter rare earths are generally magnetic. The compound ErRh1.1Sn3.6 exhibits reentrant superconductivity with Tc = 0.97 K and Tm = 0.57 K as determined from ac magnetic susceptibility measurements. The synthesis and X-ray characterization of the series are described and the results of electrical resistivity, upper critical magnetic field, magnetic susceptibility, specific heat and neutron scattering measurements on the Er compound are given. © 1980.