Multicritical End Point of the First-Order Ferromagnetic Transition in Colossal Magnetoresistive Manganites

L. Demkó, I. Kézsmárki, G. Mihály, N. Takeshita, Y. Tomioka, and Y. Tokura

Phys. Rev. Lett. 101, 037206 – Published 18 July 2008

Abstract

We have studied the bandwidth–temperature–magnetic-field phase diagram of ${RE}_{0.55} {Sr}_{0.45} {MnO}_{3}$ colossal magnetoresistance manganites with ferromagnetic metal (FM) ground state. The bandwidth was controlled both via chemical substitution and hydrostatic pressure with a focus on the vicinity of the critical pressure $p^{*}$ where the character of the zero-field FM transition changes from first to second order. Below $p^{*}$ the first-order FM transition extends up to a critical magnetic field. It approaches zero on the larger bandwidth side where the surface of the first-order FM phase boundary is terminated by a multicritical end point. The change in the character of the transition and the decrease of the colossal magnetoresistance effect is attributed to the reduced charge-order and orbital-order fluctuations.

Received 30 November 2007

DOI:https://doi.org/10.1103/PhysRevLett.101.037206

Authors & Affiliations

L. Demkó^1,2, I. Kézsmárki^1,2,3, G. Mihály¹, N. Takeshita⁴, Y. Tomioka⁴, and Y. Tokura^2,3,4

¹Department of Physics, Budapest University of Technology and Economics and Condensed Matter Research Group of the Hungarian Academy of Sciences, 1111 Budapest, Hungary
²Multiferroics Project, ERATO, Japan Science and Technology Agency (JST), Tsukuba 305-8562, Japan
³Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
⁴Correlated Electron Research Center (CERC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan

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Vol. 101, Iss. 3 — 18 July 2008

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Images

Figure 1
Bandwidth-temperature phase diagram of ${RE}_{0.55} {AE}_{0.45} {MnO}_{3}$ manganites near half-doping with a high level of quenched disorder (reproduced from Tomioka et al. [6]). In contrast to the low-disorder case where $T_{CO}$ and $T_{C}$ meet each other and form the so-called bicritical point as represented by dashed lines, the ordered phases are suppressed and an intermediate spin-glass phase appears below $T_{G}$ . The phase boundaries corresponding to the high- and low-disorder case are shown for the two series, $AE = Sr$ and $AE = Ca$ . In the present Letter the bandwidth of the FM phase was controlled over the highlighted region.Reuse & Permissions
Figure 2
Mapping procedure of the pressure–temperature–magnetic-field phase diagram of ${Sm}_{0.55} {Sr}_{0.45} {MnO}_{3}$ by magnetization and resistivity measurements. Panels (a) and (b) show the temperature dependence of the magnetization and resistivity, respectively, in various magnetic fields. Above the critical field (temperature), $H_{cr}$ ( $T_{cr}$ ) the hysteresis vanishes and the temperature-induced (field-induced) transition becomes a crossover. The corresponding curves are plotted by dashed lines. Panels (c) and (d) display the field dependence of the magnetization at various temperatures and the temperature dependence of the resistivity at selected hydrostatic pressures, respectively.Reuse & Permissions
Figure 3
Left side: Pressure dependence of the FM transition temperature for $({Sm}_{1 - x} {Nd}_{x})_{0.55} {Sr}_{0.45} {MnO}_{3}$ ( $x = 0$ , 0.2, 0.4, 0.5) in zero field. The first- and second-order PI-FM phase boundarise are plotted by dashed and full lines, respectively, while the multicritical end point separating them is labeled by a large full circle. Right upper and lower panel: Hysteresis width observed in the zero-field temperature loops of the resistivity and magnetization curves/critical magnetic field as a function of pressure. The zero-pressure position of the different compounds is indicated by large symbols with ${Sm}_{0.55} {Sr}_{0.45} {MnO}_{3}$ as the origin of the pressure scales.Reuse & Permissions
Figure 4
Upper panel: PM-FM transition overthe pressure–magnetic-field–temperature phase diagram of $({Nd}_{x} {Sm}_{1 - x})_{0.55} {Sr}_{0.45} {MnO}_{3}$ . Dashed and solid lines represent the zero-field first-order and second-order PM-FM transition, respectively. The dash-dotted line corresponds to the finite-field critical end line terminated by the multicritical end point labeled by the large circle. The surface bordered by the dashed and dash-dotted lines represent the first-order PI-FM phase boundary, as obtained by interpolation of the data points. Lower panel: Width of the temperature hysteresis over the pressure–magnetic-field plane.Reuse & Permissions

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