LOW-TEMPERATURE SPECIFIC HEAT OF YMn₂ IN THE PARAMAGNETIC AND ANTIFERROMAGNETIC PHASES

Abstract

The low-temperature specific heat of YMn2 has been measured at applied pressures of 0 to 7.7 kbar. A paramagnetic state is stabilized for moderate values of the applied pressure (of the order of 1.6 kbar). A large linear term in the specific heat, which decreases regularly with increasing pressure, is observed in this phase. It is ascribed to giant spin fluctuations associated with a magnetic-non magnetic instability and a strong geometrical spin frustration.

Quasi-One-Dimensional Spin Dynamics in d-Electron Heavy-Fermion Metal Y1-xScxMn2

“…The obtained values are consistent with earlier literature values (reported γ values for x = 0.03 and 0.08), and much greater than that predicted by band calculation (∼ 9 mJ/K 2 mol), where m * is close to that in the case of UPt 3 [9,13,14]. A similar mass enhancement was observed in YMn 2 under hydrostatic pressure to suppress the structural transition below ∼100 K, indicating that the Sc substitution corresponds to chemical pressure [10,15]. The general trend of reduced γ as well as the magnetic susceptibility χ (Fig.…”

“…It comprises a three-dimensional network of corner-shared tetrahedra with Mn ions at their corners, providing a stage equivalent to the cubic pyrochlore lattice. Although YMn 2 exhibits magnetic order with complex helical modulation and a large volume expansion below T N ∼100 K [6], it remains in a paramagnetic state under hydrostatic pressure (≥ 0.4 GPa) [7] or upon the substitution of Y by Sc (Y 1−x Sc x Mn 2 , with x ≥ 0.03) [8] which is also accompanied by a large increase in QP mass (m * ∼15 times the band mass) as inferred from the electronic specific heat [9,10]. Despite studies focused onto identifying the origin of the heavy-QP state, the issue still stands as a major challenge that has increased in importance with the succeeding discovery of LiV 2 O 4 .…”

Quest for the Origin of Heavy Fermion Behavior ind-Electron Systems

“…It shows a broad distribution with a peak near q ≃ 0 and a tail over the region |q| ≤ ∼1 Å −1 . A similar result is observed for the [1][2][3][4][5][6][7][8][9][10] direction, indicating that Eq. ( 7) can be approximated by the form…”

“…Dashed curves show λ for greater external magnetic fields (∝ ω µ ). also accompanied by a large increase in the QP mass (m * ≃ 15 times the band mass) as inferred from the electronic specific heat 2 .…”

55MnNQR/NMR studies of the magnetic properties ofYMn2under pressure

“…7 A recent neutron experiment on a Y 0.97 Sc 0.03 Mn 2 single crystal has revealed a wave-vector-dependent SF in the paramagnetic state at T ϭ10 K. 8 Also, YMn 2 shows heavy-fermion-like behavior. Its electronic specific heat coefficient ␥ is 140 mJ K Ϫ2 mol Ϫ1 in Sc-substituted material 9 and under pressure, 10 which is larger by one order of magnitude than that of ordinary d-electron systems including high-T c cu-prates. The ratio A/␥ 2 , where A is the coefficient of the quadratic contribution to the electric resistivity, is also close to that for heavy fermions.…”