Browsing by Author "Santiago, J.M."

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    Band Jahn-Teller structural phase transition inﾠY2In
    (American Physical Society, 2018) Svanidze, E.; Georgen, C.; Hallas, A.M.; Huang, Q.; Santiago, J.M.; Lynn, J.W.; Morosan, E.
    The number of paramagnetic materials that undergo a structural phase transition is rather small, which can perhaps explain the limited understanding of the band Jahn-Teller mechanism responsible for this effect. Here we present a structural phase transition observed in paramagnetic Y2In at temperature T0=250±5 K. Below T0, the high-temperature hexagonal P63/mmc phase transforms into the low-temperature orthorhombic Pnma phase. This transition is accompanied by an unambiguous thermal hysteresis of about 10 K, observed in both magnetic susceptibility M/H(T) and resistivity ρ(T), indicating a first-order transition. Band structure calculations suggest a band Jahn-Teller mechanism, during which the degeneracy of electron bands close to the Fermi energy is broken. We establish that this structural phase transition does not have a magnetic component; however, the possibility of a charge density wave formation has not been eliminated.
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    Pressure effects in the itinerant antiferromagnetic metal TiAu
    (American Physical Society, 2017) Wolowiec, C.T.; Fang, Y.; McElroy, C.A.; Jeffries, J.R.; Stillwell, R.L.; Svanidze, E.; Santiago, J.M.; Morosan, E.; Weir, S.T.; Vohra, Y.K.; Maple, M.B.
    We report the pressure dependence of the Néel temperature T N up to P ≈ 27 GPa for the recently discovered itinerant antiferromagnet (IAFM) TiAu. The T N ( P ) phase boundary exhibits unconventional behavior in which the Néel temperature is enhanced from T N ≈ 33 K at ambient pressure to a maximum of T N ≈ 35 K occurring at P ≈ 5.5 GPa. Upon a further increase in pressure, T N is monotonically suppressed to ∼ 22 K at P ≈ 27 GPa. We also find a crossover in the temperature dependence of the electrical resistivity ρ in the antiferromagnetic (AFM) phase that is coincident with the peak in T N ( P ) , such that the temperature dependence of ρ = ρ 0 + A n T n changes from n ≈ 3 during the enhancement of T N to n ≈ 2 during the suppression of T N . Based on an extrapolation of the T N ( P ) data to a possible pressure-induced quantum critical point, we estimate the critical pressure to be P c ≈ 45 GPa.
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    Quantum critical point in the Sc-doped itinerant antiferromagnet TiAu
    (American Physical Society, 2017) Svanidze, E.; Besara, T.; Wang, J.K.; Geiger, D.; Prochaska, L.; Santiago, J.M.; Lynn, J.W.; Paschen, S.; Siegrist, T.; Morosan, E.
    We present an experimental realization of a quantum critical point in an itinerant antiferromagnet composed of nonmagnetic constituents, TiAu. By partially substituting Ti with Sc in Ti 1 − x Sc x Au , a doping amount of x c = 0.13 ± 0.01 induces a quantum critical point with minimal disorder effects. The accompanying non-Fermi liquid behavior is observed in both the resistivity ρ ∝ T and specific heat C p / T ∝ − ln T , characteristic of a two-dimensional antiferromagnet. The quantum critical point is accompanied by an enhancement of the spin fluctuations, as indicated by the diverging Sommerfeld coefficient γ at x = x c .