The effect of pressure on the magnetic susceptibility of RInCu₄(R = Gd, Er and Yb)

Abstract

The magnetic susceptibility of the intermetallic compounds RInCu4 (R = Gd, Er and Yb) was measured under helium gas pressure up to 2 kbar at the fixed temperatures 78, 150 and 300 K. For YbInCu4, which exhibits a first-order valence phase transition at TV40 K, the Grüneisen parameter for the Kondo energy, K-dlnTK/dlnV = -32, is large and typical for Ce-based heavy-fermion systems in magnitude but opposite in sign. The effect of atomic disorder is discussed on the basis of the data for a chemically disordered sample; the pressure effect at T = 78 K is strongly enhanced due to the spatial dispersion of pressure-sensitive TV, and hence dTV/dP = -2.0 K kbar-1 is obtained by assuming a Gaussian distribution of TV. On the basis of an extrapolation of the experimental pressure dependence, a (P,T) phase diagram is proposed for YbInCu4. Reference compounds with stable f moments, GdInCu4 and ErInCu4, show negligible pressure dependences of the susceptibility.

Specific heat of mixed valence system YbInCu4 under pressure

“…2 shows T dependence of DC P /T at various P. T V decreases in proportional to P with qT V /qP=À16. 2 K/GPa, which is the smaller value than that of previous reports BÀ20.0 K/GPa [3][4][5][6][7].…”

“…YbInCu 4 has a firstorder valence transition at T V E40 K [1][2][3][4][5][6][7] at ambient pressure. With decreasing temperature, the valence of Yb ions changes from trivalent (4f 13 , J=7/2 ) to mixedvalent state in which valence is fluctuating between trivalent and divalent (4f 14 , J=0 ).…”

Infrared dynamics ofYbIn1−xAgxCu4: Kondo scaling, sum rules, and temperature dependence

“…At low doping, a line of first order phase transitions separates a low temperature, mixed-valent phase and a high temperature local moment phase. In YbInCu 4 (x=0) at high temperature (T > T v = 42 K), the magnetic response exhibits a Curie-Weiss form with magnitude appropriate to j = 7/2 moment of Yb and a small Weiss temperature 16 Θ W ∼ −13 K, which constrains the effective Kondo temperature appropriate in this high temperature range to be comparably small in magnitude. The resistivity in this temperature range 2 is very high for a metal (ρ dc ≃ 150µΩ-cm) and together with Hall measurements indicate a very low (hole) carrier concentration 2 .…”

Pressure Effect on Yb-Based Strongly Correlated Electron Systems

“…The valence transition of YbInCu 4 strongly depends on hydrostatic pressure [7,[23][24][25][26]. By applying pressure above P C ≈ 2.45 GPa, the low-temperature intermediate valence (IV) phase is suppressed below 2.5 K and a new magnetically ordered phase appears below T M ≈ 2.4 K [7,2].…”