Method for Analyzing Second-Order Phase Transitions: Application to the Ferromagnetic Transition of a Polaronic System

Souza, J. A.; Yu, Yi‐Kuo; Neumeier, J. J.; Terashita, H.; Jardim, R. F.

doi:10.1103/physrevlett.94.207209

Cited by 51 publications

(60 citation statements)

References 24 publications

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“…The physical meaning of λ is embodied in the Ehrenfest-like expression, dT N /dP = ν/λ, where ν is the molar volume [42]. Measurements of α-Mn under applied pressure have obtained [32] dT N /dP −20 K GPa C P (T ) data exhibit a feature around T N that is reminiscent of the analogous feature in Ω displayed in Fig.…”

Section: Original Papermentioning

confidence: 91%

“…In general, features in specific heat C P (T ) and ΩT which are associated with a second-order phase transition are expected to scale with one another as C * P (T ) = λΩT where C * P (T ) is just C P (T ) after subtracting a linear background and λ is a scaling parameter [42]. The physical meaning of λ is embodied in the Ehrenfest-like expression, dT N /dP = ν/λ, where ν is the molar volume [42].…”

Section: Original Papermentioning

confidence: 99%

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Thermal expansion and thermodynamic characterization of antiferromagnetic phase transition in elementalα-Mn

White

Bollinger

Neumeier

2014

Phys. Status Solidi B

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High‐resolution measurements of thermal expansion and specific heat have been performed on α‐Mn. An analysis of these thermodynamic properties, with particular emphasis on their behavior in the temperature region near the Néel temperature, TN = 101.4(2) K, suggests that the antiferromagnetic phase transition is continuous (second order within the Ehrenfest classification scheme). The thermal expansion for T≲TN is negative, which is probably related to the volume dependence of the magnetic exchange interactions. This is manifested in the negative pressure derivative normaldTN/normaldP and may also be related to the anomalously low reported values of the bulk modulus for α‐Mn. Large, negative values of the bulk Grüneisen function, γG, for T< 75 K are comparable to those of antiferromagnetic Cr. In each case, the magnetic contribution to γG dominates for T≤TN.

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Section: Original Papermentioning

confidence: 91%

Section: Original Papermentioning

confidence: 99%

Thermal expansion and thermodynamic characterization of antiferromagnetic phase transition in elementalα-Mn

White

Bollinger

Neumeier

2014

Phys. Status Solidi B

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“…The singularity in heat capacity around a phase transition originates from a non- analytic term in the thermodynamic free energy and can be asymptotically described 41 by a function of the form…”

Section: B Heat Capacity and Thermal Expansion Measurements And Analmentioning

confidence: 99%

“…41,42 The subscripts denote values of the parameters above (+) and below (−) T N . The value for α can be determined from the C P data by plotting log(C * P −B ± −Dt) against log(t ) and adjusting fit parameter values until the regions above and below the phase transition become linear, with similar slopes.…”

Section: B Heat Capacity and Thermal Expansion Measurements And Analmentioning

confidence: 99%

Local and long-range magnetic order of thespin−32systemCoSb2O6

et al. 2015

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The Co 2+ ions of CoSb2O6 exhibit local magnetic order below ∼80 K followed by long-range antiferromagnetic order below TN = 13.45 K. Analysis of the magnetic susceptibility above TN using an Ising model of Co-Co dimers, yields a magnetic exchange coupling J /kB = −10.603(6) K (kB is the Boltzmann constant). The transition at TN is accompanied by a spin gap in the heat capacity (∆2/kB = 33.92(9) K). Highly anisotropic behavior of the thermal expansion is observed, and the influence of local magnetic order is evident. A critical exponent of α = 0.103(3) is obtained from analysis of the critical behavior of the heat capacity and thermal expansion near TN , similar to the value expected for the three dimensional Ising universality class.

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“…Despite considerable efforts to understand the inter-play between spin, charge and lattice degrees of freedom in the CMR effect for the various materials, see e.g. [7][8][9][10][11][12], no general picture has evolved yet. For the manganites, in particular, the reason for that may be related to their complexity due to the simultaneous action of strong crystal-electric field (CEF) and Jahn-Teller (JT) effects.…”

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confidence: 99%

Lattice Strain Accompanying the Colossal Magnetoresistance Effect inEuB6

et al. 2014

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The coupling of magnetic and electronic degrees of freedom to the crystal lattice in the ferromagnetic semimetal EuB6, which exhibits a complex ferromagnetic order and a colossal magnetoresistance (CMR) effect, is studied by high-resolution thermal expansion and magnetostriction experiments. EuB6 may be viewed as a model system, where pure magnetism-tuned transport and the response of the crystal lattice can be studied in a comparatively simple environment, i.e., not influenced by strong crystal-electric field effects and Jahn-Teller distortions. We find a very large lattice response, quantified by (i) the magnetic Grüneisen parameter, (ii) the spontaneous strain when entering the ferromagnetic region and (iii) the magnetostriction in the paramagnetic temperature regime. Our analysis reveals that a significant part of the lattice effects originates in the magnetically-driven delocalization of charge carriers, consistent with the scenario of percolating magnetic polarons. A strong effect of the formation and dynamics of local magnetic clusters on the lattice parameters is suggested to be a general feature of CMR materials.Materials, in which the resistivity exhibits drastic changes in response to an external magnetic field, are of great interest both from a fundamental as well as a technological point of view. Those anomalous magnetotransport effects are particularly strongly pronounced close to a combined magnetic and insulator-metal transition, where a large or even a colossal magnetoresistance (CMR) can be observed. Prominent examples include magnetic semiconductors, rare-earth chalcogenides, silicides and hexaborides, Mn-based pyrochlors, as well as the mixed-valent rare-earth manganites [1][2][3][4][5]. One route for describing the CMR effect involves the formation of magnetic polarons (MPs). This concept was first suggested based on experiments on Eu 1−x Gd x Se [1] and shortly thereafter given a theoretical foundation [6]. MPs are formed when it is energetically favorable for the charge carriers to localize and spin polarize the surrounding local moments over a finite distance. With increasing magnetic field, these ordered clusters may grow in size, accompanied by a progressive alignment of the spins outside the ordered clusters thereby facilitating the charge transport. The existence of magnetic clusters (tantamount to MPs) in some manganites has been demonstrated by a concomitant lattice distortion, the field dependence of which closely follows the magnetoresistivity [7]. Despite considerable efforts to understand the inter- * Present address: Dept. of Physics, Indian Institute of Technology, New Dehli, India † Present address: IGCE, Unesp.-Univ. Estadual Paulista, Dept.de Física, Rio Claro, Brazil ‡ Email: j.mueller@physik.uni-frankfurt.de play between spin, charge and lattice degrees of freedom in the CMR effect for the various materials, see e.g. [7][8][9][10][11][12], no general picture has evolved yet. For the manganites, in particular, the reason for that may be related to their complexity due to t...

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Method for Analyzing Second-Order Phase Transitions: Application to the Ferromagnetic Transition of a Polaronic System

Cited by 51 publications

References 24 publications

Thermal expansion and thermodynamic characterization of antiferromagnetic phase transition in elementalα-Mn

Thermal expansion and thermodynamic characterization of antiferromagnetic phase transition in elementalα-Mn

Local and long-range magnetic order of thespin−32systemCoSb2O6

Lattice Strain Accompanying the Colossal Magnetoresistance Effect inEuB6

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