Colloquium 2006

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  Scalar order: possible scenario for certain skutterudite compounds
  
  
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  Dr. Annamaria Kiss
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  Recent experimental results suggest that in PrFe4P12, PrRu4P12 and SmRu4P$12 skutterudites the cubic symmetry is preserved even in the ordered phase. It seems that in the Sm-case the order breaks the time reversal symmetry, therefore, the pseudo-scalar T_{xyz} octupole order is a good candidate. On the other hand, in the Pr-cases the order does not break the time-reversal, staggered dipoles in the ordered phase appear only when the magnetic field is non-zero.
  We discuss the general properties of a scalar order which preserves the point group symmetry. We focus on anisotropy effects in main thermodynamical quantities at low magnetic fields and discuss the ^31P NMR spectra. We show that the scalar order can explain most of the properties of PrFe4P12 like (i) the absence of field induced dipoles perpendicular to the direction of the magnetic field, (ii) isotropy of the magnetic susceptibility independent of the field direction, (iii) the field angle dependence of the transition temperature (iv) and the main properties of the measured ^31P NMR spectra. The possibility of the pseudo-scalar T_{xyz} octupole order in SmRu4P12 is discussed briefly.
  
  
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