Mesoscopic Thermodynamics of an Inhomogeneous Colossal-Magnetoresistive Phase

Merithew, R. D.; Weissman, M. B.; Hess, F. M.; Spradling, P.; Nowak, E. R.; O’Donnell, Jim; Eckstein, J. N.; Tokura, Y.; Tomioka, Y.

doi:10.1103/physrevlett.84.3442

Cited by 92 publications

(95 citation statements)

References 13 publications

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“…[1][2][3][4]11 While these regions have typical sizes of tens nanometer, they can also form clusters of several hundred nanometers. As was documented in noise measurements, 12 muon spin relaxation 13 and in neutron-scattering experiments, 14 this phase separation is dynamic, but much slower than it is typical for critical fluctuations. By applying magnetic field, a considerable fraction of semiconducting regions can be converted into metallic regions, resulting in metallic percolation paths throughout the sample.…”

Section: Introductionmentioning

confidence: 60%

Griffiths phase, metal-insulator transition, and magnetoresistance of doped manganites

Krivoruchko¹,

Марченко²,

Melikhov

2010

Phys. Rev. B

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A phenomenological model is developed for systematic study of the universal features in metal-insulator transition and magnetoresistivity of mixed-phase manganites. The approach is based on utilization of some hypothesis appropriate to the Preisach picture of the magnetization process for half-metallic ferromagnets and an assumption that in doped manganites a Griffiths-type phase exists just above the magnetic-ordering temperature. Within the model, the system is considered as a random three-dimensional resistor network where a self-consistent formation of paths with metal and polaron types of conductivity is not only due to magnetic field variation but also due to temperature changes, as well. Both mechanisms of intrinsic percolation transition are considered on one basis. The theory is able to replicate the basic regularities found experimentally for doped manganites resistivity dependence on temperature and magnetic field without the need for empirical input from the magnetoresistive data. Within the approach a natural basis has arisen for a qualitative classification of magnetoresistive materials into those, such as La 0.7 Sr 0.3 MnO 3 , showing modest magnetoresistivity, and those, such as La 0.7 Ca 0.3 MnO 3 , showing large magnetoresistivity.

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Section: Introductionmentioning

confidence: 60%

Griffiths phase, metal-insulator transition, and magnetoresistance of doped manganites

Krivoruchko¹,

Марченко²,

Melikhov

2010

Phys. Rev. B

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“…To more closely investigate this we compare 10 seconds of high resolution resistance vs time data taken randomly from each of the 4 cycles at 45 kHz [ figure 3]. In cycles 1, 2 and 4 we see clear indications of single domain transitions as regular resistive jumps occur 20,26 . The regularity of the resistive levels within each of the cycles are consistent with a percolative transport network in which a single electronic phase domain transitions between charge ordered insulating (COI) and ferromagnetic metallic (FMM) phases thereby creating discrete resistive levels.…”

Section: A Thermal Cycling Effects On Electronic Domainsmentioning

confidence: 99%

Dynamics of a first-order electronic phase transition in manganites

et al. 2011

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By reducing an electronically phase separated manganite (La 1-y Pr y ) x Ca 1-x MnO 3 single crystal thin film to dimensions on the order of the inherent phase domains, it is possible to isolate and monitor the behavior of single domains at a first order transition. At this critical point, it is possible to study the coexistence, formation and annihilation processes of discrete electronic phase domains. With this technique, we make several new observations on the mechanisms leading to the metal insulator transition in manganites. We observe that domain formation is emergent and random, the transition process from the metallic phase to the insulating phase takes longer than the reverse process, electric field effects are more influential in driving a phase transition than current induced electron heating, and single domain transition dynamics can be tuned through careful application of temperature and electric field.

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“…The shoulder in the zero-field curve arises from the tail in c(0, T ) in the vicinity of T C . This may signal a break-down in the effective medium approximation, as very large clusters are known from noise measurements [24,30] to have a dramatic effect on the zero-field resisitivity near the transition. The self-consistent values m(H, 18 K), shown as open circles in the inset of Fig.…”

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confidence: 99%

Colossal Magnetoresistance is a Griffiths Singularity

2002

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It is now widely accepted that the magnetic transition in doped manganites that show large magnetoresistance is a type of percolation effect. This paper demonstrates that the transition should be viewed in the context of the Griffiths phase that arises when disorder suppresses a magnetic transition. This approach explains unusual aspects of susceptibility and heat capacity data from a single crystal of La0.7Ca0.3MnO3.The term "colossal magnetoresistance" (CMR) has commonly been used to describe the very large, magneticfield driven changes in electrical resistivity in oxides based on LaMnO 3 near their second-order, ferromagnetic transitions. The largest CMR effects are accompanied by other anomalies in magnetic and thermodynamic properties. Among these are the failure of the magnetic correlation length to increase strongly as the transition temperature T C is approached from above, the persistence of a well defined spin-wave dispersion close to the transition [1], and an unusual shift in the heat capacity peak to higher temperatures in applied magnetic fields.[2] An explanation of this unusual behavior of the heat capacity in the context of a Griffiths singularity [3] is the focus of the present paper.There is now general consensus that the CMR transition is a type of percolation in which, due to the doubleexchange process [4], bonds become metallic as neighboring spins tend to align. The strength of the CMR effect (along with the transition temperature) depends strongly on the ionic size and concentration of the divalent atom that substitutes for La in LaMnO 3 . The effect is nearly absent for La 2/3 Sr 1/3 MnO 3 (T C = 360 K) but quite strong in the present sample La 0.7 Ca 0.3 MnO 3 (T C = 218 K) [5]. In the low temperature metallic phase, the exchange interactions, as measured by the spin-wave stiffness, are the same in Sr-snd Ca-doped crystals [6], demonstrating that the key to the CMR effect is to be found in the non-metallic regime. The ionic size of the divalent substituent exerts its effect on magnetic and electronic properties through local tilting of the oxygen octahedra [7] and the concurrent bending of the active Mn-OMn bonds. This inhibits the formation of metallic bonds and leads to charge localization, polaron formation, and possible charge segregation [8,9]. Evidence in favor of a percolation picture comes from a Monte-Carlo simulation of a random field Ising model that assigns conductivity zero and unity to bonds between neighboring antiparallel and parallel spins respectively [10]. It both produces CMR and emphasizes the importance of randomness. Experimental evidence was provided by Jaime et al.[11] who extracted the field and temperature dependent metallic-bond concentration c(H, T ) from the resistivity via the effective medium approximation, and showed that it also describes the thermoelectric power data. Direct evidence for coexisting polaronic/insulating and metallic components have been reported from neutron [12] Discussions of the CMR effect in percolation terms [16][17][18] have gener...

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Mesoscopic Thermodynamics of an Inhomogeneous Colossal-Magnetoresistive Phase

Cited by 92 publications

References 13 publications

Griffiths phase, metal-insulator transition, and magnetoresistance of doped manganites

Griffiths phase, metal-insulator transition, and magnetoresistance of doped manganites

Dynamics of a first-order electronic phase transition in manganites

Colossal Magnetoresistance is a Griffiths Singularity

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