What we believe to be the first experimental results have been obtained on strong magnetic x-ray dichroism in the $M_{4,5}$ absorption spectra of magnetically ordered rare-earth materials, in accordance with recent predictions.

Diluted magnetic semiconductors have received much attention due to their potential applications for spintronics devices. A prototypical system (Ga,Mn)As has been widely studied since the 1990s. The simultaneous spin and charge doping via hetero-valent (Ga³⁺,Mn²⁺) substitution, however, resulted in severely limited solubility without availability of bulk specimens. Here we report the synthesis of a new diluted magnetic semiconductor (Ba_1−xK_x)(Zn_1−yMn_y)₂As₂, which is isostructural to the 122 iron-based superconductors with the tetragonal ThCr₂Si₂ (122) structure. Holes are doped via (Ba²⁺, K¹⁺) replacements, while spins via isovalent (Zn²⁺,Mn²⁺) substitutions. Bulk samples with x=0.1−0.3 and y=0.05−0.15 exhibit ferromagnetic order with T_C up to 180 K, which is comparable to the highest T_C for (Ga,Mn)As and significantly enhanced from T_C up to 50 K of the ‘111’-based Li(Zn,Mn)As. Moreover, ferromagnetic (Ba,K)(Zn,Mn)₂As₂ shares the same 122 crystal structure with semiconducting BaZn₂As₂, antiferromagnetic BaMn₂As₂ and superconducting (Ba,K)Fe₂As₂, which makes them promising for the development of multilayer functional devices.

Strong geometrical frustration in magnets leads to exotic states such as spin liquids, spin supersolids, and complex magnetic textures. SrCu₂(BO₃)₂, a spin-1/2 Heisenberg antiferromagnet in the archetypical Shastry–Sutherland lattice, exhibits a rich spectrum of magnetization plateaus and stripe-like magnetic textures in applied fields. The structure of these plateaus is still highly controversial due to the intrinsic complexity associated with frustration and competing length scales. We discover magnetic textures in SrCu₂(BO₃)₂ via magnetostriction and magnetocaloric measurements in fields up to 100.75 T. In addition to observing low-field fine structure with unprecedented resolution, the data also reveal lattice responses at 73.6 T and at 82 T that we attribute, using a controlled density matrix renormalization group approach, to a unanticipated 2/5 plateau and to the long-predicted 1/2 plateau.

Recent neutron scattering and specific heat studies on the pyrochlore Yb2Ti2O7 have revealed variations in its magnetic behavior below 265 mK. In the best samples, a sharp anomaly in the specific heat is observed at T=265~mK. Other samples, especially single crystals, have broad features in the specific heat which vary in sharpness and temperature depending on the sample, indicating that the magnetic ground state may be qualitatively different in such samples. We performed detailed comparisons of the chemical structure of a pulverized single crystal of Yb2Ti2O7, grown by the floating zone technique, to a sintered powder sample of Yb2Ti2O7. Rietveld refinements of neutron powder diffraction data on these samples reveal that the crushed single crystal is best described as a ``stuffed'' pyrochlore, Yb2(Ti2$-${}xYbx)O7$-${}x/2 with x~= 0.046(4), despite perfectly stoichiometric starting material. Substituting magnetic Yb3+ on the nonmagnetic Ti4+ sublattice would introduce random exchange bonds and local lattice deformations. These are expected to be the mechanism leading to the variation of the delicate magnetic ground state of Yb2Ti2O7. Determination of the cubic cell length a could be useful as a method for characterizing the stoichiometry of nonpulverized single crystals at room temperature.

The transverse field Ising chain model is ideally suited for testing the fundamental ideas of quantum phase transitions because its well-known $T=0$ ground state can be extrapolated to finite temperatures. Nonetheless, the lack of appropriate model materials hindered the past effort to test the theoretical predictions. Here, we map the evolution of quantum fluctuations in the transverse field Ising chain based on nuclear magnetic resonance measurements of ${\mathrm{CoNb}}_2{\mathrm{O}}_6$, and we demonstrate the finite-temperature effects on quantum criticality for the first time. From the temperature dependence of the ${}^{93}\mathrm{Nb}$ longitudinal relaxation rate $1/T_1$, we identify the renormalized classical, quantum critical, and quantum disordered scaling regimes in the temperature ($T$) vs transverse magnetic field ($h_{\perp }$) phase diagram. Precisely at the critical field $h_{\perp }^c=5.25\pm 0.15\mathrm{T}$, we observe a power-law behavior, $1/T_1\sim T^{-3/4}$, as predicted by quantum critical scaling. Our parameter-free comparison between the data and theory reveals that quantum fluctuations persist up to as high as $T\sim 0.4J$, where the intrachain exchange interaction $J$ is the only energy scale of the problem.