We have measured the electrical resistivity, Hall effect, and magnetization of a Nd B6 single crystal, in a temperature range from 2 to 300 K, and in magnetic fields of up to 7 T. We find that the low-field Hall resistivity varies strongly with temperature. This variation arises entirely from the large anomalous Hall effect we find in Nd B6. In the paramagnetic region, the anomalous Hall coefficient is much larger than the ordinary one and is independent of temperature. As the antiferromagnetic order sets in, below ∼8 K, it decreases sharply with decreasing temperature. We do not find any significant variations of the anomalous Hall coefficient in the neighborhood of the critical point. Both magnetization and Hall resistivity show an anomaly in low magnetic fields, which may arise from domain rotations. © 2005 The American Physical Society.

We present a two-fluid description of the Kondo lattice that is based on an analysis of CeCoIn5 at various levels of dilution with La. We show that thermal and transport measurements provide evidence for the survival of the Kondo impurity component in the lattice as T-->0 K, and that the evolution of the low temperature properties of the Kondo lattice can be viewed as the partial condensation of the lattice of Kondo centers into a heavy fermion fluid. The resulting two-fluid model is shown to be applicable to the general problem of the ground state of the Kondo lattice.

Single crystals of YbAlB4 were grown in excess Al flux. Plate- and needle-shaped crystals were found. The plates are found to be ß-YbAlB4, which crystallizes with the ThMoB4 structure type in space group Cmmm (No. 65), Z = 4, with lattice parameters of a = 7.3080(4), b = 9.3150(5), and c = 3.4980(2) Å. The needle-shaped crystals were identified as the first form of YbAlB4 which crystallizes with the YCrB4 structure type in space group Pbam (No. 55), Z = 4, with lattice parameters of a = 5.9220(2), b = 11.4730(3), and c = 3.5060(5) Å. While both compounds have heavy fermion ground states with Isinglike magnetic anisotropy, the electronic specific heat coefficients (γ) differ. The ß-phase has a γ value near 300 mJ mol -1 K-2, more than twice that of the α-phase, γ = 130 mJ mol-1 K-2. A comparison of the structures and physical properties of both polymorphs is presented. © 2007 American Chemical Society.

Single crystals of Ce2PdGa12 have been synthesized in Ga flux and characterized by X-ray diffraction. This compound crystallizes in the tetragonal P4/nbm space group, Z=2 with lattice parameters of a=6.1040(2)Å and c=15.5490(6)Å. It shows strongly anisotropic magnetism and orders antiferromagnetically at TN∼11 K. A field-induced metamagnetic transition to the ferromagnetic state is observed below TN. Structure-property relationships with the related heavy-fermion antiferromagnet CePdGa6 are discussed. © 2005 Elsevier Inc. All rights reserved.

When a polarized light beam is incident upon the surface of a magnetic material, the reflected light undergoes a polarization rotation¹. This magneto-optical Kerr effect (MOKE) has been intensively studied in a variety of ferro- and ferrimagnetic materials because it provides a powerful probe for electronic and magnetic properties^{2, 3} as well as for various applications including magneto-optical recording⁴. Recently, there has been a surge of interest in antiferromagnets (AFMs) as prospective spintronic materials for high-density and ultrafast memory devices, owing to their vanishingly small stray field and orders of magnitude faster spin dynamics compared to their ferromagnetic counterparts^5-9. In fact, the MOKE has proven useful for the study and application of the antiferromagnetic (AF) state. Although limited to insulators, certain types of AFMs are known to exhibit a large MOKE, as they are weak ferromagnets due to canting of the otherwise collinear spin structure^10-14. Here we report the first observation of a large MOKE signal in an AF metal at room temperature. In particular, we find that despite a vanishingly small magnetization of M ~0.002 µ_B/Mn, the non-collinear AF metal Mn₃Sn¹⁵ exhibits a large zero-field MOKE with a polar Kerr rotation angle of 20 milli-degrees, comparable to ferromagnetic metals. Our first-principles calculations have clarified that ferroic ordering of magnetic octupoles in the non-collinear Néel state¹⁶ may cause a large MOKE even in its fully compensated AF state without spin magnetization. This large MOKE further allows imaging of the magnetic octupole domains and their reversal induced by magnetic field. The observation of a large MOKE in an AF metal should open new avenues for the study of domain dynamics as well as spintronics using AFMs.

We use scanning tunneling microscopy to elucidate the atomically resolved electronic structure in the strongly correlated kagome Weyl antiferromagnet Mn_{3}Sn. In stark contrast to its broad single-particle electronic structure, we observe a pronounced resonance with a Fano line shape at the Fermi level resembling the many-body Kondo resonance. We find that this resonance does not arise from the step edges or atomic impurities but the intrinsic kagome lattice. Moreover, the resonance is robust against the perturbation of a vector magnetic field, but broadens substantially with increasing temperature, signaling strongly interacting physics. We show that this resonance can be understood as the result of geometrical frustration and strong correlation based on the kagome lattice Hubbard model. Our results point to the emergent many-body resonance behavior in a topological kagome magnet.