Competition between magnetism and superconductivity inTmNi2B2C

Tm169Mössbauer-spectroscopy study of the magnetic superconductor TmNiMulders1, Gubbens2, Buschow3 1996Phys. Rev. B11060View full textAdd to dashboardCite

“…13 These authors observe that TmNi 2 B 2 C is as effective in magnetic pair breaking as GdNi 2 B 2 C and they conclude that the crystal-field levels in TmNi 2 B 2 C are close together so they all contribute to the pair-breaking process. ϩ SR established the magnetic c-axis anisotropy in TmNi 2 B 2 C. [4][5][6] The temperature dependence of QS(T) also indicates that B 2 0 is negative, that is approximately Ϫ1 to Ϫ1.7 K. This value is smaller than B 2 0 ϭϪ2.8͑5͒ K as it is calculated above. Most likely, the empirical relation V zz latt ϭ Ϫ4cB 2 0 /␣ J ͗r 2 ͘ with cϭ185, is not valid in this compound due to the carbon atoms which are interstitially present in the crystal nearby the Tm atoms.…”

“…A detailed analysis of QS(T), combined with specificheat measurements, may turn out to be conclusive. Third, line broadening is observed above 1 K, persisting up to ϳ40 K. This line broadening might correspond to ϩ SR results, where a muon precession signal is observed up to ϳ30 K. 4,5 Both these features indicate slow magnetic relaxation above the Néel temperature.…”

“…1͑b͔͒ is observed which decreases with increasing temperature and persists up to about 40 K. At present, its origin is not yet obvious. It might correspond to the phenomenon seen in ϩ SR studies [4][5][6] where the ϩ precession frequency persists up to high temperatures compared with T N . Magnetic relaxation of the Tm moments above T N could explain our Möss-bauer spectra as well as the ϩ SR data if the relaxation is sufficiently slow ͑Ͼ10 Ϫ6 s͒.…”

“…Over the past few years, the RNi 2 B 2 C compounds ͑Rϭrare earth͒ have been the subject of different studies including magnetization, 1 specific heat, 2 inelastic neutron scattering, 3 and ϩ SR. [4][5][6] In some of these compounds ͑R ϭTm, Er, and Ho͒ these studies revealed the coexistence of superconductivity and magnetism. As the strength of the exchange interaction between R atoms increases ͑De Gennes scaling͒ the transition to the superconducting state occurs at lower temperatures, due to the increase of magnetic Cooper pair breaking.…”

Rare-earth metal transition metal borocarbide and nitridoborate superconductors

“…The effect of deviations from the ideal composition within the (small) homogeneity range has been studied, e.g., for TmNi 2 [B 2 C]: 169 Tm Mößbauer spectroscopy [204,205] as well as mSR measurements [205][206][207][208] were derived from unit cell parameters, EDX, metallographic investigations and thermal analysis, which have an important effect on physical properties. Indeed, even small deviations of both C and B content yield disappearance of the superconducting properties [116].…”