Electronic Properties of Magnetic Superconductor HoNi₂B₂C Under High Pressure

Abstract

The electrical resistivity of single crystalline HoNi 2 B 2 C has been measured at high pressure and magnetic fields. The three anomalies in the magnetoresistance due to metamagnetic transitions are observed both at ambient and high pressures. It is found that the metamagnetic transition fields increase with increasing pressure. The temperature dependence of electrical resistivity is strongly dependent on magnetic field. Non Fermi liquid behavior is observed near the metamagnetic transition fields. But the normal Fermi liquid behavior recovers after completing the phase transition. The Grüneisen parameters are also calculated to examine the stability of electronic state.

Effect of pressure on the superconducting properties and magnetism in HoNi2B2C

“…T N increases with pressure, ∂T N /∂P = +0.41 K/GPa. Compared with the previous data [2,4], ∂T C (offset)/∂P = −0.46 to − 0.50 K/GPa and ∂T N /∂P = 0.70-0.84 K/GPa, the present results show that the pressure derivative of T C (offset) is nearly the same but that of T N is different. The origins of the difference are partly due to an experimental error but not clear now.…”

“…3 displays the pressure dependence of T C (onset), T C (offset), T AF C1 , T AF C2 and T N . Below 2.5 GPa, the re-entrant peak in the ρ(T ) curve does not appear at H = 0, but is seen at small applied magnetic field, H = 1.5 kOe [4]. T N , T AF C1 and T AF C2 are obtained at H = 1.5 kOe.…”

“…This is caused by the antiferromagnetic correlation of 4f-electrons enhanced by applying pressure to give magnetic interaction to overcome the superconductivity. Compressibility of this compound has large anisotropy; linear compressibility of c-axis is two times larger than that of a-axis [4]. This fact implies that the distance between layers shrinks more than that in the layers.…”

Magnetotransport in the magnetic superconductor HoNi2B2C

“…The temperature dependence of electrical resistivity also depends strongly on magnetic field in the paramagnetic state [7,8]. Such behavior has been observed in some heavy-fermion compounds, where several kinds of interactions such as RKKY interaction, the Kondo effect and CEF effect are competing each other [9,10].…”

“…A magnetic phase diagram is described by the results of magnetoresistance, mangetization and heat capacity, indicating a complex magnetic structure at low temperature and magnetic field [4][5][6]. In the paramagnetic phase at high temperature, on the other hand, the magnetic properties of HoNi 2 B 2 C is dominated by Ho 3+ ion, which is influenced not only by the total angular momentum but also by the crystal electric field (CEF).The temperature dependence of electrical resistivity also depends strongly on magnetic field in the paramagnetic state [7,8]. Such behavior has been observed in some heavy-fermion compounds, where several kinds of interactions such as RKKY interaction, the Kondo effect and…”