title: Doped YbRh2Si2: not only ferromagnetic correlations but ferromagnetic order.
abstract: YbRh2Si2 is a prototypical system for studying unconventional antiferromagnetic quantum criticality. However, ferromagnetic correlations are present which can be enhanced via isoelectronic cobalt substitution for rhodium in Yb(Rh(1-x)Co(x))2Si2. So far, the magnetic order with increasing x was believed to remain antiferromagnetic. Here, we present the discovery of ferromagnetism for x = 0.27 below T(C) = 1.30  K in single crystalline samples. Unexpectedly, ordering occurs along the c axis, the hard crystalline electric field direction, where the g factor is an order of magnitude smaller than in the basal plane. Although the spontaneous magnetization is only 0.1 μB/Yb it corresponds to the full expected saturation moment along c taking into account partial Kondo screening.
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids, D-01187 Dresden, Germany. lausberg@cpfs.mpg.de
authors.forename: S
authors.initials: S
authors.lastname: Lausberg
authors.forename: A
authors.initials: A
authors.lastname: Hannaske
authors.forename: A
authors.initials: A
authors.lastname: Steppke
authors.forename: L
authors.initials: L
authors.lastname: Steinke
authors.forename: T
authors.initials: T
authors.lastname: Gruner
authors.forename: L
authors.initials: L
authors.lastname: Pedrero
authors.forename: C
authors.initials: C
authors.lastname: Krellner
authors.forename: C
authors.initials: C
authors.lastname: Klingner
authors.forename: M
authors.initials: M
authors.lastname: Brando
authors.forename: C
authors.initials: C
authors.lastname: Geibel
authors.forename: F
authors.initials: F
authors.lastname: Steglich