RT Journal Article
SR Electronic
T1 Ferromagnetic Quantum Critical Point in the Heavy-Fermion Metal YbNi<sub>4</sub>(P<sub>1−</sub><em><sub>x</sub></em>As<em><sub>x</sub></em>)<sub>2</sub>
JF Science
JO Science
FD American Association for the Advancement of Science
SP 933
OP 936
DO 10.1126/science.1230583
VO 339
IS 6122
A1 Steppke, Alexander
A1 Küchler, Robert
A1 Lausberg, Stefan
A1 Lengyel, Edit
A1 Steinke, Lucia
A1 Borth, Robert
A1 Lühmann, Thomas
A1 Krellner, Cornelius
A1 Nicklas, Michael
A1 Geibel, Christoph
A1 Steglich, Frank
A1 Brando, Manuel
YR 2013
UL http://science.sciencemag.org/content/339/6122/933.abstract
AB Unconventional superconductivity and other previously unknown phases of matter exist in the vicinity of a quantum critical point (QCP): a continuous phase change of matter at absolute zero. Intensive theoretical and experimental investigations on itinerant systems have shown that metallic ferromagnets tend to develop via either a first-order phase transition or through the formation of intermediate superconducting or inhomogeneous magnetic phases. Here, through precision low-temperature measurements, we show that the Grüneisen ratio of the heavy fermion metallic ferromagnet YbNi4(P0.92As0.08)2 diverges upon cooling to T = 0, indicating a ferromagnetic QCP. Our observation that this kind of instability, which is forbidden in d-electron metals, occurs in a heavy fermion system will have a large impact on the studies of quantum critical materials.