Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 45: Correlated Electrons: Poster Session
TT 45.2: Poster
Donnerstag, 29. März 2012, 15:00–19:00, Poster B
Magnetic properties of Yb(Rh1−xCox)2Si2 with x=0.58 — •A. Haase1, O. Stockert1, C. Klingner1, C. Krellner1, S. Matas2, M. Brando1, C. Geibel1, and F. Steglich1 — 1Max-Planck-Institut CPfS, Dresden, Germany — 2Helmholtz-Zentrum Berlin, Berlin, Germany
The heavy-fermion compound YbRh2Si2 is an ideal model system to study quantum criticality. Due to its very low antiferromagnetic ordering temperature TN ≈ 70 mK and the small ordered magnetic moment, the magnetic structure of YbRh2Si2 is still unknown. Isoelectronic doping with Co leads to an increase of the ordering temperature TN and of the ordered magnetic moment. The (x - T) - phase diagram of Yb(Rh1−xCox)2Si2 shows a marked dip in the ordering temperature TN near a Co concentration of about 50%. This may indicate a change of magnetic structure. For x > 0.58 the magnetic structure is incommensurate below TN with a propagation vector τ1 = (0.25 0.08 1) followed by a change to a commensurate structure at a lower TL with τ2 = (0.25 0.25 1). For x = 0.58 only the commensurate magnetic order was found below T ≈ 750 mK up to now. For lower Co-concentrations the magnetic structure is still unknown. To study the change of magnetic structure in more detail, we performed magnetisation, heat capacity and resistivity measurements on Yb(Rh0.42Co0.58)2Si2, which is near the minimum in the (x - T) - phase diagram. While in zero magnetic field heat capacity and resistivity measurements reveal only one phase transition at TN ≈ 800 mK, a second transition was detected in the magnetisation at T = 650 mK and B < 0.2 T.