Tom A. Bither

New Modified Mn2Sb Compositions Showing Exchange Inversion

Transformations from ferrimagnetic to antiferromagnetic ordering with decreasing temperature have now been observed in manganese antimonides modified with V, Co, Cu, Zn, Ge, and As as well as with Cr. The magnetic structure change is accompanied by a first‐order change in the volume of the unit cell as well as a change in electrical resistivity. Crystallographic data for these materials in the exchange inversion region and at room temperature are presented as a function of the concentration of modifying element.

Palladium and platinum phosphochalcogenides—Synthesis and properties

Abstract Three new PdPyS2−y (0 P 3 m1 ) was also obtained at autogenous pressure. The crystal structure of this semiconductor was solved by refinement of X-ray powder intensity data using trial and error methods. Reactivity was much lower in the related Pt systems and only substitution of small amounts of S for P in pyrite-type PtP2 was observed.

Mixed-cation transition metal pyrite dichalcogenides—High pressure synthesis and properties

Abstract Ternary, pyrite-type dichalcogenides Zn y Mn 1− y X 2 , Cd y Mn 1− y X 2 , Zn y Cd 1− y X 2 , Zn y Cu 1− y X 2 , Cd y Cu 1− y X 2 , Mn y Cu 1− y X 2 , Cu ∼0.75 Fe ∼0.25 S 2 , and Ni 0.4–0.6 Fe 0.6-0.4 X 2 (0 y 2 was elevated upon substitution with less than 20 a/o of Zn or Cd. A noncolinear spin structure is proposed to explain the ferromagnetism observed in the Mn y Cu 1− y X 2 compounds.

Exchange Inversion in Mn2−xCrxSb

Compounds of the form Mn2−xCrxSb show a first-order ferrimagnetic to antiferromagnetic phase transition with decreasing temperature. Sublattices composed of the three adjacent ferrimagnetically aligned (001) planes Mn(II)-Mn(I)-Mn(II) are ferromagnetically ordered above the transition temperature Ts and antiferromagnetically ordered below Ts. The exchange interaction between these sublattices changes sign at a critical interlayer distance. The discontinuous change in interlayer distance at Ts is proportional to the square of the magnetization of the sublattice in agreement with Kittels conclusions.

Nitrato- and fluoroboracites M3B7O13NO3 and M3B7O13F

Abstract New boracites containing nitrato- or fluoroanions that appear to be true low-pressure phases have been synthesized at superatmospheric pressures. The M3B7O13NO3 compounds (M = Co, Ni, Cu, Zn, Cd) transform rapidly and reversibly in the temperature region 300–500°C between probable orthorhombic and face centered cubic symmetry, while the M3B7O13F compounds (M = Mg, Mn, Fe, Co, Zn) appear to maintain rhombohedral symmetry up to their decomposition temperatures of 800–900°C. True high-pressure boracite-like phases containing F and Cr, Mn, Fe, or Co that decompose upon heating to M3B7O13F have also been isolated.

Magnetic and electrical properties of ternary pyrite-type CrxCo1−xS2 phases prepared at high pressure

New pyrite-type phases CrxCo1−xS2 (0 < x < 0.4) have been prepared at 65 kbars pressure in a tetrahedral anvil apparatus. Magnetic measurements indicate that the saturation magnetization decreases, while the Curie temperature increases, with increasing x. Tc reaches a maximum above room temperature at x ⋍ 0.3. The magnetic data favor an arrangement in which low-spin Cr+2 is aligned antiferromagnetically to Co+2. Electrical measurements show essentially temperature-independent resistivity with ϱ ⋍ 10−4 ohm-cm.