D. Aoki

Similarity of the Fermi surface in the hidden order state and in the antiferromagnetic state of URu₂Si₂.

Shubnikov-de Haas measurements of high quality URu2Si2 single crystals reveal two previously unobserved Fermi surface branches in the so-called hidden order phase. Therefore, about 55% of the enhanced mass is now detected. Under pressure in the antiferromagnetic state, the Shubnikov-de Haas frequencies for magnetic fields applied along the crystalline c axis show little change compared with the zero pressure data. This implies a similar Fermi surface in both the hidden order and antiferromagnetic states, which strongly suggests that the lattice doubling in the antiferromagnetic phase due to the ordering vector Q(AF)=(001) already occurs in the hidden order. These measurements provide a good test for existing or future theories of the hidden order parameter.

Tricritical point and wing structure in the itinerant ferromagnet UGe

Precise resistivity measurements on the ferromagnetic superconductor UGe2 under pressure p and magnetic field H reveal a previously unobserved change of the anomaly at the Curie temperature. Therefore, the tricritical point (TCP) where the paramagnetic-to-ferromagnetic transition changes from a second order to a first order transition is located in the p-T phase diagram. Moreover, the evolution of the TCP can be followed under the magnetic field in the same way. It is the first report of the boundary of the first order plane which appears in the p-T-H phase diagram of weak itinerant ferromagnets. This line of critical points starts from the TCP and will terminate at a quantum critical point. These measurements provide the first estimation of the location of the quantum critical point in the p-H plane and will inspire similar studies of the other weak itinerant ferromagnets.

Interplay of magnetism, Fermi surface reconstructions, and hidden order in the heavy-fermion material URu 2 Si 2

URu

High-field metamagnetism in the antiferromagnet CeRh 2 Si 2

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High-field moment polarization in the ferromagnetic superconductor UCoGe

Si

Transverse and longitudinal magnetic-field responses in the Ising ferromagnets URhGe, UCoGe, and UGe2

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Skutterudite Results Shed Light on Heavy Fermion Physics

is surely one of the most mysterious of the heavy-fermion compounds. Despite more than 20 years of experimental and theoretical works, the order parameter of the transition at

Field-induced Phenomena in Ferromagnetic Superconductors UCoGe and URhGe

{T}_{0}=17.5

Lifshitz transition and metamagnetism: Thermoelectric studies ofCeRu2Si2

K is still unknown. The state below

Magnetic field evolution of critical end point in UGe2

{T}_{0}