Magnetic properties of RT2Zn20 R = rare earth, T = Fe, Co , Ru, Rh , Os and Ir

Single crystals of RT2Zn20 compounds were grown from Zn self-flux. Thermodynamic and transport measurements indicated that YFe2Zn20 is closer to the Stoner criteria. As a result of local moments embedded in this highly polarizable Fermi liquid, remarkably high-temperature ferromagnetic ordering was found for RFe 20Zn20 (R = Gd - Tm). Furthermore, pseudo-ternary compounds GdxY1-xFe2Zn20 manifest ferromagnetic ordering above 1.8 K for Gd concentrations x\u3e0.02. In contrast, for the isostructural RCo2Zn20 series, only Gd and Tb compounds manifest antiferromagnetic ordering above 2 K, correspondent a \u27normal metal\u27 behavior of YCo2Zn 20. Six Yb compounds (YbT2Zn20, T = Fe, Co, Ru. Rh, Os and Ir) were proved to be heavy fermion compounds associated with different Fermi liquid state

Large Magnetoresistance in Compensated Semimetals TaAs2_2 and NbAs2_2

We report large magnetoresistance (MR) at low temperatures in single-crystalline nonmagnetic compounds TaAs$_2$ and NbAs$_2$. Both compounds exhibit parabolic-field-dependent MR larger than $5\times10^3$ in a magnetic field of 9 Tesla at 2 K. The MR starts to deviate from parabolic dependence above 10 T and intends to be saturated in 45 T for TaAs$_2$ at 4.2 K. The Hall resistance measurements and band structural calculations reveal their compensated semimetal characteristics. The large MR at low temperatures is ascribed to a resonance effect of the balanced electrons and holes with large mobilities. We also discuss the relation of the MR and samples' quality for TaAs$_2$ and other semimetals. We found that the magnitudes of MR are strongly dependent on the samples' quality for different compounds.Comment: 26 pages, 11 figures, 2 table

Quantum Interactions in Topological R166 Kagome Magnet

Kagome magnet has been found to be a fertile ground for the search of exotic quantum states in condensed matter. Arising from the unusual geometry, the quantum interactions in the kagome lattice give rise to various quantum states, including the Chern-gapped Dirac fermion, Weyl fermion, flat band and van Hove singularity. Here we review recent advances in the study of the R166 kagome magnet (RT6E6, R = rare earths; T = transition metals; and E = Sn, Ge, etc.) whose crystal structure highlights the transition-metal-based kagome lattice and rare-earth sublattice. Compared with other kagome magnets, the R166 family owns the particularly strong interplays between the d electrons on the kagome site and the localized f electrons on the rare-earth site. In the form of spin-orbital coupling, exchange interaction and many-body effect, the quantum interactions play an essential role in the Berry curvature field in both the reciprocal and real spaces of R166 family. We discuss the spectroscopic and transport visualization of the topological electrons hosted in the Mn kagome layer of RMn6Sn6 and the various topological effects due to the quantum interactions, including the Chern-gap opening, the exchange-biased effect, the topological Hall effect and the emergent inductance. We hope this work serves as a guide for future explorations of quantum magnets.Comment: Submitted versio