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TT: Fachverband Tiefe Temperaturen

TT 54: Correlated Electrons: Heavy Fermions

TT 54.4: Vortrag

Mittwoch, 2. April 2014, 10:15–10:30, HSZ 204

Magnetic phases in the heavy-fermion system Yb(Rh_1−xCo_x)₂Si₂ — •A. Hannaske¹, O. Stockert¹, C. Klingner¹, N. Mufti¹, C. Krellner², A. Hoser³, J.-U. Hoffmann³, S. Matas³, S. Capelli⁴, M.-H. Lemee-Cailleau⁴, K. Kaneko⁵, M. Brando¹, C. Geibel¹, and F. Steglich¹ — ¹Max-Planck-Institut CPfS, Dresden, Germany — ²Goethe-Universität Frankfurt, Frankfurt a. M., Germany — ³Helmholtz-Zentrum Berlin, Berlin, Germany — ⁴Institut Laue-Langevin, Grenoble, France — ⁵Japan Atomic Energy Agency, Tokai, Japan

One route to get insight into the unusual magnetic properties of quantum critical YbRh₂Si₂ is to study magnetism in the alloying series Yb(Rh_1−xCo_x)₂Si₂. Isoelectronic doping of Co on the Rh site leads to a stabilization of the magnetic order. The magnetic phases in Yb(Rh_1−xCo_x)₂Si₂ have been investigated in detail by thermodynamic measurements and neutron scattering. In pure YbCo₂Si₂ the occurrence of antiferromagnetic domains plays an important role in understanding the magnetic B−T phase diagram. While for Yb(Rh_1−xCo_x)₂Si₂ with high Co content our measurements clearly reveal an incommensurate magnetically ordered phase below T_N followed by a commensurate phase at low T, the magnetic order drastically changes below about x ≈ 0.58 where surprisingly ferromagnetic behavior was observed. We will discuss this finding and its impact on the quantum criticality in YbRh₂Si₂.