Electronic Structure and Related Properties of Rare Earth Transition Metal Borocarbides -LDA Bandstructure Analysis

Rösner, H.; Drechsler, S.‐L.; Koepernik, Klaus; Opahle, Ingo; Eschrig, H.

doi:10.1007/978-94-010-0763-4_7

Cited by 1 publication

(3 citation statements)

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“…These slow electrons have a strong el-ph coupling and are responsible for the superconductivity. Noteworthily, slow electrons in LuNi 2 B 2 C and YNi 2 B 2 C stem from nested regions on the FS whereas in the nonsuperconducting compound LaNi 2 B 2 C there is no nesting and, consequently, a smaller dispersion of v F (Rosner et al 2001). The dispersion of v F in YNi 2 B 2 C has been confirmed by de Haas van Alphen experiments (Goll et al 1996).…”

Section: The Upper Critical Fieldmentioning

confidence: 71%

“…A possible reason for the very large positive MR in LuNi 2 B 2 C and for the significantly larger MR of the polycrystalline sample (Narozhnyi et al 1999a) compared with single-crystal data (Rathnayaka et al 1997) is the formation of open orbits on the FS of that compound for H ⊥ c. (When a magnetic field is applied, the resulting electron orbits may be closed or open depending upon the topology of the FS.) The possibility of the formation of open orbits for borocarbides was pointed out by Kim et al (1995), and Rosner et al (2001). It is well known (Lifshitz et al 1973) that open orbits can lead to large values of MR ∼ H 2 , whereas closed orbits should give rise to saturation of MR for large H .…”

Section: Magnetotransportmentioning

confidence: 94%

“…Total and partial density of states calculated for YNi 2 B 2 C, using the local density approximation. The Fermi level E F is at zero energy(Rosner et al 2001).…”

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confidence: 99%

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Interaction of superconductivity and magnetism in borocarbide superconductors

2001

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The interaction of rare-earth magnetism and superconductivity has been a topic of interest for many years. In classical magnetic superconductors (Chevrel phases, ternary rhodium borides, etc) as well as in the high-T c cuprates the superconducting state usually coexists with antiferromagnetic order on the rare-earth sublattice. In these compounds the magnetic ordering temperature T N is much below the superconducting transition temperature T c . The discovery of superconducting borocarbides RT 2 B 2 C with R = Sc, Y, La, Th, Dy, Ho, Er, Tm or Lu and T = Ni, Ru, Pd or Pt (where not all of these combinations of R and T result in superconductivity) has reanimated the research on the coexistence of superconductivity and magnetic order. Most of these borocarbides crystallize in the tetragonal LuNi 2 B 2 C type structure which is an interstitial modification of the ThCr 2 Si 2 type. Contrary to the behaviour of Cu in the cuprates Ni does not carry a magnetic moment in the borocarbides. Various types of antiferromagnetic structures on the rare-earth sublattice have been found to coexist with superconductivity in RNi 2 B 2 C for R = Tm, Er, Ho and Dy. Particularly of interest is the case of HoNi 2 B 2 C for which three different types of antiferromagnetic structures have been observed: (i) a commensurate one with Ho moments aligned ferromagnetically within layers perpendicular to the tetragonal c axis where consecutive layers are aligned in opposite directions, (ii) an incommensurate spiral along the c axis and (iii) an incommensurate a-axismodulated structure with a modulation vector τ ≈ (0.55, 0, 0). This wave vector emerges in various RNi 2 B 2 C compounds with magnetic as well as nonmagnetic R elements and is connected with Fermi surface nesting. Both incommensurate magnetization structures have been shown to be related to the near-reentrant behaviour observed in HoNi 2 B 2 C whereas the commensurate structure coexists well with the superconducting state in this compound. The variation of T N and T c with the de Gennes factor can roughly be drawn on straight lines from Lu to Gd and from Lu to Tb, respectively, with the exception of Yb. Consequently, T c > T N holds for Tm, Er, Ho and T c < T N for Dy. However, the study of various pseudoquaternary (R, R )Ni 2 B 2 C compounds has shown that this so-called de Gennes scaling is not universal for the borocarbides and it breaks down in some cases, which is attributed to effects of details

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Section: The Upper Critical Fieldmentioning

confidence: 71%

Section: Magnetotransportmentioning

confidence: 94%