Magnetic, specific heat and electrical transport properties of Frank–Kasper cage compounds RTM₂Al₂₀[R  =  Eu, Gd and La; TM  =  V, Ti]

Abstract

Abstract. Single crystals of Frank-Kasper compounds RTM 2 Al 20 (R = Eu, Gd and La; TM = V and Ti) were grown by self-flux method and their physical properties were investigated through magnetization (M ), magnetic susceptibility (χ), specific heat (C P ) and electrical resistivity (ρ) measurements. Powder x-ray diffraction studies and structural analysis showed that these compounds crystallize in the cubic crystal structure with the space group F d3m. The magnetic susceptibility for the compounds EuTi 2 Al 20 and GdTi 2 Al 20 showed a sudden jump below the Néel temperature T N indicative of plausible double magnetic transition. Specific heat (C P ) and electrical resistivity (ρ) measurements also confirm the first-order magnetic transition (FOMT) and possible double magnetic transitions. Temperature variation of heat capacity showed a sharp phase transition and huge C P value for the (Eu/Gd)Ti 2 Al 20 compounds Full width at half-maximum (FWHM) < 0.2 K) which is reminiscent of a first-order phase transition and a unique attribute among RTM 2 Al 20 compounds. In contrast, linear variation of C P is observed in the ordered state for (Eu/Gd)V 2 Al 20 compounds suggesting a λ-type transition. We observed clear anomaly between heating and cooling cycle in temperature-time relaxation curve for the compounds GdTi 2 Al 20 (2.38 K) and EuTi 2 Al 20 (3.2 K) which is indicating a thermal arrest due to the latent heat. The temperature variation of S mag for GdTi 2 Al 20 saturates to a value 0.95R ln 8 while the other magnetic systems exhibited still lower entropy saturation values in the high temperature limit. (C P − γT )/T 3 vs T plot showed a maximum near 27 K for all the compounds indicating the presence of low frequency Einstein modes of vibrations. Resistivity measurements showed that all the samples behave as normal Fermi liquid type compounds and ρ(T ) due to electron-phonon scattering follows Bloch-Grüneisen-Mott relation in the paramagnetic region.

Evolution of Physical Properties of RE3Ni5Al19Family (RE = Y, Nd, Sm, Gd, Tb, Dy, Ho, and Er)

“…The anomaly at 20 K is sharp, and the heating–cooling curve across the transition (marked as gray area) shows a change of slope (Figure S2b, Supporting Information), confirming the first order character of a transition. [ 23 ] All three anomalies shift toward lower temperatures only with applied field of 9 T.…”

First-principles investigations on structural stability, mechanical, and thermodynamic properties of La T 2 Al 20 ( T = Ti, V, Cr, Nb, and Ta) intermetallic cage compounds

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15] In the meantime, some ternary AT 2 Al 20 intermetallics systems (where A = actinide/lanthanide/calcium and T = transition metal) were synthesized with CeCr 2 Al 20type structure. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Kangas and Thiede synthesized the new LaT 2 Al 20 (T = Ti, V, Cr, Nb, and Ta) intermetallics by using a step-wise arc melting technique and by self-flux method. [31,32] For these new LaT 2 Al 20 phases, although their intrinsic physical properties have been explored, their mechanical properties and thermodynamics properties are not clarified.…”