Magnetic properties of CeB6, PrB6, EuB6, and GdB6

Abstract

The results of a study of the magnetic properties of the hexaborides of cerium, praseodymium, europium, and gadolinium at temperatures from 7 to 300 °K are reported. The susceptibility of CeB6 obeys a Curie‐Weiss law, χ = C/(T – θ), above 200 °K with a moment of 2.51 μβ and θ = −82 °K. PrB6 obeys a Curie‐Weiss law above 100 °K with a moment of 3.64 μβ and θ = −41 °K. The reciprocal susceptibility of PrB6 shows a minimum at 8.3 °K associated with an antiferromagnetic transition. Europium hexaboride is ferromagnetic at low temperatures with a Curie point of 8.8 °K. The initial reciprocal susceptibility in the range from 9 to 14 °K varies at (T – TC)1,20. Above 30 °K the susceptibility of EuB6 accurately obeys a Curie‐Weiss law with θ = −0.5 °K and μeff = 7.90 μβ. Magnetization curves and isotherms of σ2 vs. H/σ are given for EuB6 for temperatures just above the Curie point. The susceptibility of GdB6 obeys a Curie‐Weiss law above 70 °K with θ = −66.5 °K and μeff = 7.98 μβ. Further, an antiferromagnetic transition exists at (16.4 ± 0.2) °K. Finally, X‐ray diffraction data were obtained for the four compounds yielding lattice constants of 4.140 Å, 4.131 Å, 4.175 Å, and 4.109 Å for CeB6, PrB6, EuB6, and GdB6 respectively.

Anisotropy of the Charge Transport in GdB6

“…1b). This transition which phase boundary H 1 (T ) has nearly horizontal view was observed previously in the range H 1 ≈ 0.4 ÷ 0.7 T from magnetization and torque measurements [2,3,5] performed on single(poly-) crystals of GdB 6 of a various quality. Besides the character of H 1 (T ) curve probably corresponds to some field induced magnetization processes.…”

“…Gadolinium hexaboride (GdB 6 ) is the S-state system (for Gd 3+ , L = 0, S = 7/2) which represents very unusual physical properties [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Similar to another rare earth (RE) hexaborides GdB 6 crystallizes in a simple bcc structure of CsCl type (s.g. P m3m−O 1 h ) and shows the flat phonon dispersion relations around 10 meV [15] corresponding to the motion of RE ions inside a rigid boron cage.…”

“…GdB 6 demonstrates two successive first-order antiferromagnetic (AF) transitions with simultaneous structural distortions to AF I [or H] state at T N 1 ≈ 15 K and to AF II [or L] state below T N 2 . (The value of T N 2 is found to be strongly sample dependent ranging in the interval T N 2 ≈ 5−10 K [1][2][3][4][5][6][7][8][9][10][11][12][13][14]). Recent structural investigations (including X-ray [8][9][10][11][12] and neutron diffraction [13,14] experiments) have shown that commensurate magnetic structure with the wave vector k m = [1/4, 1/4, 1/2] is realized both in AF I and AF II states of GdB 6 .…”

Rediscovering the Crystal Chemistry of Borides

“…For hexaborides, the antiferromagnetic ordering stems from the coupling between the conduction band and the 4f electrons; [325] there is one free electron per each trivalent metal. [326] Thus, divalent europium in ferromagnetic EuB 6 is the exception. Admittedly, the ordering in europium hexaboride is more complicated than a simple valence electron count, as it possesses two magnetic transitions.…”

Mg‐Assisted Autoclave Synthesis of RB6 (R = Sm, Eu, Gd, and Tb) Submicron Cubes and SmB6 Submicron Rods

“…Rare-earth hexaborides have attracted much attention because of their various peculiar properties such as high melting point, high hardness, high chemical stability, superconductivity, [1,2] magnetic properties, [3][4][5] high efficiency thermionic emission, and narrow-band semiconductivity, and so forth. [6][7][8][9][10] Therefore, rare-earth hexaborides have great technical importance and their synthesis is significant.…”