Pressure-tuned first-order phase transition and accompanying resistivity anomaly inCeZn1−δSb2

Abstract

The Kondo lattice system CeZn0.66Sb2 is studied by electrical resistivity and ac magnetic susceptibility measurements at several pressures. At P = 0 kbar, ferromagnetic and antiferromagnetic transitions appear at 3.6 and 0.8 K, respectively. The electrical resistivity at TN dramatically changes from the Fisher-Langer type (ferromagnetic like) to the Suezaki-Mori type near 17 kbar, i.e., from a positive divergence to a negative divergence in the temperature derivative of the resistivity. The pressure-induced SM type anomaly, which shows thermal hysteresis, is easily suppressed by small magnetic field (1.9 kOe for 19.8 kbar), indicating a weakly first-order nature of the transition. By subtracting a low-pressure data set, we directly compare the resistivity anomaly with the SM theory without any assumption on backgrounds, where the negative divergence in dρ/dT is ascribed to enhanced critical fluctuations in the presence of superzone gaps.PACS numbers: 68.35. Rh, 71.27.+a, 72.15.Qm, 75.20.Hr Rare-earth and actinide compounds with localized felectrons at high temperatures show non-magnetic or even a superconducting ground state, which cannot be explained by Hill's observation that magnetic ordering depends on the f -atom spacing: magnetism at large f − f spacing and paramagnetism or superconductivity at small separation.1 The importance of s − f exchange coupling J between localized f -electrons and conduction band electrons for determining the ground state, which was neglected by Hill, is typified in heavy-electron, Kondo-lattice, or mixed-valence systems, where a paramagnetic or a superconducting ground state is observed even though they have large f − f spacing.2,3 Depending on the hybridization strength |JN F |, the ground state is determined through competition between Kondo and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions, where N F is the conduction band density-of-states at the Fermi energy E F . For |JN F | << 1, a magnetic state is stabilized because the RKKY interaction that provides coupling between local moments depends geometrically on |J| -T RKKY ∝ J 2 N F , whereas a Kondo singlet is preferred for large JN F because the Kondo interaction that screens local moments depends exponentially on |J| -T K ∝ exp(−1/|J|N F ). 4Another important consequence of the exchange interaction between the localized and conduction electrons is a change in the electronic structure. When an antiferromagnetic structure (AF) with a period incommensurate with the ionic lattice appears, the magnetic superlattice may distort the Fermi surface dramatically, 5 forming magnetic superzone gaps below T N when the ordering wavevector K A connects portions of the Fermi surface.6 Suezaki and Mori (SM) showed that, when combined with enhanced spin scattering in a K = K A mode in antiferromagnets, this sharp band gap gives rise to a sharp increase in the resistivity or a negative divergence in the temperature derivative near T N .7 Early measurements on rare-earth metals and order-disorder systems revealed a similar resistivity ...

Magnetism in ordered metallic perovskite compound

“…7(a) and (b)]. Such an increase in r values below T N has been mainly attributed to the opening of AFM superzone gap [17,18]. Super-zone gap appears due to the presence of AFM magnetic-structure incommensurate with the periodicity of crystal lattice [17,18].…”

“…Such an increase in r values below T N has been mainly attributed to the opening of AFM superzone gap [17,18]. Super-zone gap appears due to the presence of AFM magnetic-structure incommensurate with the periodicity of crystal lattice [17,18]. In that, the magnetic superlattice distorts the Fermi surface leading to the formation of an energy gap in the conduction band that affects the electrical transport and results in sharp increase of r below T N .…”

“…In most of the cases the effects of super-zone gap can be suppressed by the application of external magnetic fields [17,18]. This collapse of super-zone gap in the presence of external magnetic field suppresses the r values below T N and thus leads to negative magnetoresistance.…”

“…In that, the magnetic superlattice distorts the Fermi surface leading to the formation of an energy gap in the conduction band that affects the electrical transport and results in sharp increase of r below T N . This effect reflects in the negative divergence of temperature derivative of r (dr=dT) below T N [17,18].…”

Magnetism and transport studies in off-stoichiometric metallic perovskite compounds GdPd3Bx (x=0.25, 0.50 and 0.75)

“…7(a)). This behavior can be attributed to the effect of opening of superzone gap in the conduction band due to the presence of a magneticlattice incommensurate with the periodicity of crystal-lattice [7,13,14]. In general, application of external magnetic field suppresses the effect of superzone gap [7,9].…”