Magnetism and superconductivity in (RE) Ni2B2C: The case of TmNi2B2C

Kulić, Miodrag L.; Buzdin, A. I.; Bulaevskiǐ, L. N.

doi:10.1016/s0375-9601(97)00568-9

Cited by 7 publications

(3 citation statements)

References 21 publications

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“…For instance, the authors of Ref. [36] point towards the possible existence of a line of nodes in the superconducting gap in the antiferromagnetic phase of TmNi 2 B 2 C. We have now ruled out this possibility.…”

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confidence: 79%

Tunneling spectroscopy in the magnetic superconductorTmNi2B2C

et al. 2001

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We present new measurements about the tunneling conductance in the borocarbide superconductor TmNi 2 B 2 C. The results show a very good agreement with weak coupling BCS theory, without any lifetime broadening parameter, over the whole sample surface. We detect no particular change of the tunneling spectroscopy below 1.5K, when both the antiferromagnetic (AF) phase and the superconducting order coexist.

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confidence: 79%

Tunneling spectroscopy in the magnetic superconductorTmNi2B2C

et al. 2001

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“…The large anisotropy between the experimental upper critical field along the a and along the c axis is not an internal property of the superconducting electron system, but is due to the large difference between the magnetic aand c-axis susceptibility of the Tm ions. Although the transformation of the Q F state into the c-axis ferromagnet did not occur, it is clear that the Anderson-Suhl mechanism plays an important role for the behavior of TmNi 2 B 2 C, see also the discussion by Kulić et al [19]. The loss in the superconducting condensation energy at the field-induced transition to the normal state is compensated for by the gain in the RKKY exchange energy deriving from the uniform magnetization because of the sudden increase of J (0).…”

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confidence: 94%

Interdependence of Magnetism and Superconductivity in the BorocarbideTmNi2B2C

et al. 2000

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We have discovered a new antiferromagnetic phase in TmNi2B2C by neutron diffraction. The ordering vector is QA = (0.48, 0, 0) and the phase appears above a critical in-plane magnetic field of 0.9 T. The field was applied in order to test the assumption that the zero-field magnetic structure at QF = (0.094, 0.094, 0) would change into a c-axis ferromagnet if superconductivity were destroyed. We present theoretical calculations which show that two effects are important: A suppression of the ferromagnetic component of the RKKY exchange interaction in the superconducting phase, and a reduction of the superconducting condensation energy due to the periodic modulation of the moments at the wave vector QA.PACS numbers: 74.70. Dd, 75.25.+z, 74.20.Fg The interplay between magnetism and superconductivity is inherently of great interest since the two phenomena represent ordered states which are mutually exclusive in most systems. Therefore, the borocarbide intermetallic quaternaries with stoichiometry (RE)Ni 2 B 2 C have attracted great attention since the publication of their discovery in 1994 [1,2], as they exhibit coexistence of magnetism and superconductivity if the rare earth (RE) is either Dy, Ho, Er or Tm. The magnetic moments in these compounds are due to the localized 4f electrons of the rare-earth ions. The 4f and the itinerant electrons are coupled weakly by the exchange interaction, resulting in the indirect Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction between the 4f -moments. Thus the RKKY interaction, which is decisive for the cooperative behavior of the magnetic electrons, depends on the state of the metallic ones.The borocarbides have a tetragonal crystal structure with space group (I4/mmm) [3], and TmNi 2 B 2 C has a superconducting critical temperature T c = 11 K and a Néel temperature T N = 1.5 K [4]. The crystalline electric field aligns the thulium moments along the c axis, and the magnetic structure has a short fundamental ordering vector Q F = (0.094, 0.094, 0) with several higher-order odd harmonics [5,6]. In the magnetic structures detected in any of the other systems, the moments of the rare-earth ions are confined to the basal plane, and they have short wavelength antiferromagnetically ordered states. For example, they are commensurate with a propagation vector Q = (0, 0, 1) for RE = Ho and Dy, or incommensurate with Q ≈ (0.55, 0, 0) for RE = Gd, Tb, Ho and Er [5]. An especially tight coupling between magnetism and superconductivity has been clearly demonstrated in TmNi 2 B 2 C, where a magnetic field applied along the c axis induced concurrent changes of the magnetic structure and the symmetry of the flux line lattice [7]. Similar effects have not yet been observed in any of the other borocarbides.One question that immediately arises, and which we believe is important for the general understanding of the interaction between superconductivity and magnetism, is why the long-period magnetic ordering found in TmNi 2 B 2 C is stable. Bandstructure calculations on the normal state of non-magne...

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“…The superconducting density of states of TmNi 2 B 2 C, however, follows nearly isotropic s-wave behavior well within the antiferromagnetic phase [34]. Magnetic diffraction of the vortex lattice has unveiled a series of transitions stemming from the close interplay between magnetism and superconductivity in both of these compounds [35][36][37][38].…”

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confidence: 99%