Magnetism and Colossal Magnetoresistance of the Pseudo-Ternary Rare-Earth Transition-Metal Compounds, Eu_14-xCa_xMnSb₁₁ (x < 3)

Abstract

The compounds, Eu14 - x Ca x MnSb11 (x < 3), have been prepared by heating the mixture of stoichiometric amounts of the elements, sealed in a quartz-jacketed Ta tube, in a two-zone furnace with T high = 1100 and T low = 1050 °C for 10 days. These compounds are isostructural with the Zintl compound Ca14AlSb11. The rare-earth transition-metal compounds crystallize in the tetragonal space group I41/acd, Z = 8, T = 90 K, a = 17.2235(7) and c = 22.6555(9) Å, V = 6720.7(5) Å3, and R 1 /wR 2 (0.0413/0.1129) for x = 1.45 and a = 17.1737(7) and c = 22.5741(10) Å, V = 6657.9(5) Å3, and R 1 /wR 2 (0.0392/0.1122) for x = 2.83. Temperature-dependent magnetic susceptibility measurement of the powder samples reveals complex magnetic interactions in the compounds and indicates a canted ferromagnetic configuration for Eu14 - x Ca x MnSb11. As the amount of nonmagnetic Ca increases to x = 2, the effective magnetic moment decreases from 29.9 to 27.9 μB/f.u., and the paramagnetic Curie temperature of the compound increases from 82.4 to 86.4 K at 1000 Oe. The magnetotransport properties of one compound, Eu13CaMnSb11 (x = 1), were measured and show a close relation to its magnetic properties, especially in the low-temperature region. The influence of chemical substitution on the structural and physical properties of Eu14 - x Ca x MnSb11 will be discussed in terms of the site preferences of Ca doping into the four different Eu sites.

Neutron Diffraction Study of the Ternary Transition Metal Zintl Compound Ca14MnSb11

“…In the hightemperature range the compound shows semiconducting behavior with r RT ¼ 6:29  10 À3 O cm, but as the temperature decreases below the magnetic transition temperature the compound exhibits metallic behavior. The transition from paramagnetic semiconducting to ferromagnetic metallic state is broad compared to the ternary rare-earth transition metal compounds of the same structure type (6,7,19). Figure 9 shows a plot of the magnetoresistance ratio ðMR ¼ ½ðrðHÞ À rð0ÞÞ=rðHÞ Â 100%Þ as a function of temperature.…”

“…The study also shows that the size of the metal cation and pnictogen element has a key role in determining the electrical and magnetic properties of the compound by changing the overlap of the anion wave functions resulting in a modified energy band gap. The continuous efforts to elucidate the magnetic properties of the compounds have been expanded to more complex systems, such as the rare-earth transition metal ternaries Eu 14 MnPn 11 (6,18,19), Yb 14 MnPn 11 (5,11), and the pseudo-ternaries Eu 14Àx A x MnSb 11 (A=Ca, Sr, Ba, Yb, Gd) (7,20,21).…”

Structure and magnetic properties of Ca14MnP11

“…In general, the structure can be understood within the Zintl formulism as composed of AlSb 4 9À tetrahedron, Sb 3 7À trimer, 4 Sb 3À anions, and 14 Ca 2+ cations. The main group-containing compounds are semiconductors and the Mn-containing compounds show unusual behavior such as long-range magnetic ordering and colossal magnetoresistance [5][6][7][8][9][10][11][12]. These magnetic properties are surprising considering that there are no possible mechanisms for orbital super-exchange and the tetrahedron are well separated.…”

Magnetotransport Properties and Kondo Effect Observed in a Ferromagnetic Single‐Crystalline Fe1−xCoxSi Nanowire

“…Ternary magnetic materials formed by doping have long been a subject of interest due to their peculiar electrical and magnetic properties in conjunction with the novel characteristics exhibited by isostructural end members. [1][2][3][4] A representative system is Fe 1Àx Co x Si with a cubic but noncentrosymmetric B20 structure. [5][6][7][8][9][10][11][12][13][14][15][16] FeSi, the parent material of Fe 1Àx Co x Si, is an archetypal Kondo material that shows unusual temperature-dependent electrical, optical, thermal, and magnetic properties, [17][18][19] whereas CoSi is a diamagnetic semimetal that shows temperature-independent magnetic susceptibility.…”