Magnetoelastic coupling in URu2Si2: Probing multipolar correlations in the hidden order state

Time-reversal symmetry and magnetoelastic correlations are probed by means of high-resolution volume dilatometry in URu 2 Si 2 at cryogenic temperatures, and magnetic fields sufficient to suppress the hidden order state at H HO ( T = 0.66 K ) ≃ 35 T. We report a significant magnetoelastic volume expansion at and above H HO ( T ) , and even above T HO , possibly a consequence of field-induced f -electron localization. We investigate in detail the magnetostriction and magnetization as the temperature is reduced across two decades in temperature from 30 K where the system is paramagnetic, to 0.5 K in the realm of the hidden order state. We find a dominant quadratic-in-field dependence Δ L / L ∝ H 2 , a result consistent with a state that is symmetric under time reversal. The data shows, however, an incipient yet unmistakable asymptotic approach to linear ( Δ L / L ∝ 1 − H / H 0 ) for 15 T < H < H HO ( 0.66 K ) ∼ 40 T at the lowest temperatures. We discuss these results in the framework of a Ginzburg-Landau formalism that proposes a complex order parameter for the HO phase to model the ( H , T , p ) phase diagram.Fil: Wartenbe, Mark. National High Magnetic Field Laboratory; Estados Unidos. Florida State University; Estados UnidosFil: Baumbach, Ryan E.. National High Magnetic Field Laboratory; Estados Unidos. Florida State University; Estados UnidosFil: Shekhter, Arkady. National High Magnetic Field Laboratory; Estados Unidos. Florida State University; Estados UnidosFil: Boebinger, Gregory S.. National High Magnetic Field Laboratory; Estados Unidos. Florida State University; Estados UnidosFil: Bauer, Eric D.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Corvalán Moya, Carolina del Huerto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Harrison, Neil. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: McDonald, Ross D.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Salamon, Myron B.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Jaime, Marcelo. Los Alamos National High Magnetic Field Laboratory; Estados Unido

Specific heat and magnetic measurements in Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3 samples

We studied the magnetization as a function of temperature and magnetic field in the compounds Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3. It allowed us to identify the ferromagnetic, antiferromagnetic and charge ordering phases in each case. The intrinsic magnetic moments of Nd3+ and Ho3+ ions experienced a short range order at low temperatures. We also did specific heat measurements with applied magnetic fields between 0 and 9 T and temperatures between 2 and 300 K in all three samples. Close to the charge ordering and ferromagnetic transition temperatures the specific heat curves showed peaks superposed to the characteristic response of the lattice oscillations. Below 10 K the specific heat measurements evidenced a Schottky-like anomaly for all samples. However, we could not successfully fit the curves to either a two level nor a distribution of two-level Schottky anomaly. Our results indicated that the peak temperature of the Schottky anomaly was higher in the compounds with narrower conduction band.Comment: submitted to PR

Magnetic nanopantograph in the SrCu[subscript 2](BO[subscript 3])[subscript 2] Shastry-Sutherland lattice

Magnetic materials having competing, i.e., frustrated, interactions can display magnetism prolific in intricate structures, discrete jumps, plateaus, and exotic spin states with increasing applied magnetic fields. When the associated elastic energy cost is not too expensive, this high potential can be enhanced by the existence of an omnipresent magnetoelastic coupling. Here we report experimental and theoretical evidence of a nonnegligible magnetoelastic coupling in one of these fascinating materials, SrCu[subscript 2](BO[subscript 3])[subscript 2] (SCBO). First, using pulsed-field transversal and longitudinal magnetostriction measurements we show that its physical dimensions, indeed, mimic closely its unusually rich field-induced magnetism. Second, using density functional-based calculations we find that the driving force behind the magnetoelastic coupling is the [^ over CuOCu] superexchange angle that, due to the orthogonal Cu[superscript 2+] dimers acting as pantographs, can shrink significantly (0.44%) with minute (0.01%) variations in the lattice parameters. With this original approach we also find a reduction of ~10% in the intradimer exchange integral J, enough to make predictions for the highly magnetized states and the effects of applied pressure on SCBO

Missing magnetism in Sr4Ru3O10: Indication for Antisymmetric Exchange Interaction

Metamagnetism occuring inside a ferromagnetic phase is peculiar. Therefore, Sr4Ru3O10, a TC = 105 K ferromagnet, has attracted much attention in recent years, because it develops a pronounced metamagnetic anomaly below TC for magnetic fields applied in the crystallographic ab-plane. The metamagnetic transition moves to higher fields for lower temperatures and splits into a double anomaly at critical fields Hc1 = 2.3 T and Hc2 = 2.8 T, respectively. Here, we report a detailed study of the different components of the magnetization vector as a function of temperature, applied magnetic field, and varying angle in Sr4Ru3O10. We discover for the first time a reduction of the magnetic moment in the plane of rotation at the metamagnetic transition. The anomaly shifts to higher fields by rotating the field from H ⊥ c to H // c. We compare our experimental findings with numerical simulations based on spin reorientation models taking into account magnetocrystalline anisotropy, Zeeman effect and antisymmetric exchange interactions. While Magnetocrystalline anisotropy combined with a Zeeman term are sufficient to explain a metamagnetic transition in Sr4Ru3O10, a Dzyaloshinskii-Moriya term is crucial to account for the reduction of the magnetic moment as observed in the experiments