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Magnetic Weyl semimetals (MWSM) have attracted significant attention due to their intriguing physical properties and potential applications in spin-electronic devices. Here we report the characterization of NdAlSi including transport, magnetization, and heat capacity on single crystals, as well as band structure calculation. It is a newly proposed MWSM candidate which breaks both time-reversal and spacial inversion symmetries. A temperature-magnetic field phase diagram is experimentally established. Remarkably, on the angular magnetoresistance (AMR), a two-fold symmetric sharp peak instead of a smooth variation is observed in the field-induced ferrimagnetic phase. We argue that the tunability of both the topological and magnetic properties in NdAlSi is crucial for realizing such a behavior. Our results indicate that 4f-electron-based MWSM can provide a unique platform to explore new and intriguing quantum phenomena arising from the interaction between magnetism and topology., 24 pages, 12 figures

Finding promising materials that show large thermoelectricity at low temperatures is crucial for low-temperature refrigeration applications. Here, we report a significantly large thermoelectric power factor ( PF) up to 50 μW cm−1 K−2 at an extremely low temperature of ∼8 K in a quasi-one-dimensional (Q1D) antiferromagnet KMn6Bi5, in which highly electrical conductivity and dramatic enhancement of Seebeck coefficient may favor its occurrence. In addition, a giant Nernst signal has also been detected with a maximum value of 24 μV K−1 T−1 at ∼5 K. All these intriguing characteristics observed in KMn6Bi5 can be attributed to the manifestation of the unusually strong coupling among spin, charge, lattice, and one dimensionality in KMn6Bi5. Our findings provide fundamental insight into the thermal transport in Q1D antiferromagnets and should stimulate further experimental exploration of thermal transport in such Q1D family for possible thermoelectric applications at extremely low temperatures.

The cubic pyrochlore Dy2Pt2O7 was synthesized under 4 GPa and 1000 °C and its magnetic and thermodynamic properties were characterized by DC and AC magnetic susceptibility and specific heat down to 0.1 K. We found that Dy2Pt2O7 does not form long-range magnetic order, but displays characteristics of canonical spin ice such as Dy2Ti2O7, including (1) a large effective moment 9.64 μ B close to the theoretical value and a small positive Curie–Weiss temperature θ CW = +0.77 K signaling a dominant ferromagnetic interaction among the Ising spins; (2) a saturation moment ∼4.5 μ B being half of the total moment due to the local 〈111〉 Ising anisotropy; (3) thermally activated spin relaxation behaviors in the low (∼1 K) and high (∼20 K) temperature regions with different energy barriers and characteristic relaxation time; and most importantly, (4) the presence of a residual entropy close to Pauling’ estimation for water ice.

Electric polarization in conventional ferroelectric oxides usually involves nonmagnetic transition-metal ions with an empty d shell (the d0 rule). Here we unravel a new mechanism for local electric dipoles based on magnetic Fe3+ (3d5) ion violating the d0 rule (Fig. 1a). The competition between the long-range Coulomb interaction and short-range Pauli repulsion in a FeO 5 bipyramid with proper lattice parameters would favor an off-center displacement of Fe3+ that induces a local electric dipole (Fig. 1b-e). The manipulation of this kind of non-d0 electric dipoles opens up a new route for generating unconventional dielectrics, ferroelectrics, and multiferroics. As a prototype example, we show that the non-d0 electric dipoles in ferrimagnetic hexaferrites (Ba, Sr)Fe 12 O 19 lead to a new family of magnetic quantum paraelectrics (Fig. 2).1