Anisotropic Near-Zero Thermal Expansion in REAg_xGa_4–x (RE = La–Nd, Sm, Eu, and Yb) Induced by Structural Reorganization

Abstract

In this work, we have discovered the anisotropic near Zero Thermal Expansion (NZTE)_ behavior in a family of compounds REAgxGa4-x (RE = LaNd , Sm, Eu and Yb). The compouds adopts CeAl2Ga2 structure type. were obtained as single crystals in high yield by metal flux growth technique using gallium as active flux. Synthesized compounds with space group I4/mmm. Temperature dependent single crystal X-ray diffraction suggests that all the compounds exhibit zero thermal expansion along c direction in the temperature range of 100-450 K. Temperature dependent X-Ray absorption near edge spectroscopic study confirmed ZTE behavior is due to the geometrical features associated within the crystal structure. The anisotropic NZTE behavior was further established by anisotropic magnetic measurements on selected single crystals. The atomic displacement parameters, apparent bond lengths, bond angles, and structural distortion with respect to the temperature reveal that geometric features associated with the structural distortion cause the anisotropic NZTE along c-direction. The preliminary magnetic studies suggest all the compounds are paramagnetic at room temperature except LaAgGa3. Electrical resistivity study reveals that compounds from this series are metallic in nature.

The Electronic and Thermodynamic Properties of Ternary Rare Earth Metal Alloys

“…They exhibit numerous structural properties [1][2]. There is a focus on structural, electronic, magnetic, and thermodynamic properties, such as fermionic, heavy-fermions [3][4], and half-metallic behavior in rare-earth intermetallic compounds such as SmInZn, SmInCd and SmTlZn [5][6], and the giant magneto-resistance device is an industrial application of heavy rare earth compounds [7][8][9]. These equal-atomic type compounds of rare earth have been investigated seriously in the last few years [10][11][12][13][14][15].…”

Diversity in Crystal Structure and Physical Properties of RETX3 (RE – Rare Earth, T – Transition Metal, X – Main Group Element) Intermetallics

“…Intermetallic compounds with the composition RETX 3 (RE -Rare Earth, T -Transition metals, X -Group 13-15 elements, except non-metals) have been studied extensively because of their structural diversity, [1,2] which leads to interesting physical properties. [3][4][5] The presence of 4f electrons in RE and the d-electrons in T and their interaction favors the generation of interesting magnetic and electronic properties such as ferromagnetism, antiferromagnetism, [6][7][8][9][10] spin-glass, [11] Kondo behavior, [8,12,13] heavy fermion behavior, [14,15] mixed valence, [16][17][18] and superconductivity. [7,[19][20][21][22][23][24] Along with physical properties some solid-state structural transformation, [18] narrow band gap semiconductor [16] The highly localized 4f electrons in rareearth atoms in "many" intermetallic compounds.…”

“…In contrast, the long-range ferromagnetic ordering is favored at lower Ga concentrations. [29] Apart from the fundamental studies rareearth based intermetallics has found their industrial applications in cryogenic magnetic refrigeration, [30,31] magnetic applications, [32] catalysis, [33][34][35][36] thermal spray coating, [37] zero thermal expansion [3,38,39] and many more.…”