High-temperature spin dynamics in CMR manganites: ESR and magnetization

Causa, M.T.; Tovar, M.; Caneiro, A.; Prado, F.; Ibañez, G.; Ramos, C.A.; Butera, A.; Alascio, B.; Obradors, X.; Piñol, S.; Rivadulla, F.; Vázquez–Vázquez, C.; López‐Quintela, M. Arturo; Rivas, J.; Tokura, Y.; Oseroff, S. B.

doi:10.1103/physrevb.58.3233

Cited by 255 publications

(206 citation statements)

References 22 publications

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“…In this so called "pseudo CE" structure the zig-zag FM chains in the ab plane are FM aligned along the c axis 10 . This is unlike the CE structure where the layers in the ab plane are aligned antiferromagnetically along c. Although several EPR studies on the manganites have been reported recently across the metal-insulator transition [14][15][16][17][18][19][20][21] , to our knowledge, there has been no study across the CO transition. The dynamics of spins in the charge ordered state as studied by EPR is expected to throw some light on the controversial magnetic structure between the charge ordering transition and the Neel temperature.…”

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confidence: 97%

An electron paramagnetic resonance study of Pr_0.6Ca_0.4MnO₃across the charge-ordering transition

Gupta¹,

Joshi²,

Bhat³

et al. 2000

J. Phys.: Condens. Matter

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We report the first electron paramagnetic resonance studies of single crystals and powders of Pr 0.6 Ca 0.4 MnO 3 in the 300-4.2 K range, covering the charge ordering transition at ∼ 240 K and antiferromagnetic transition (T N ) at ∼ 170 K. The asymmetry parameter for the Dysonian single crystal spectra shows anomalous increase at T co . Below T co the g-value increases continuously, suggesting a gradual strengthening of orbital ordering. The linewidth undergoes a sudden increase at T co and continues to increase down to T N .The intensity increases as the temperature is decreased till T co due to the renormalization of magnetic susceptibility arising from the build up of ferromagnetic correlations. The value of the exchange constant, J, is estimated to be 154 K.

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confidence: 97%

An electron paramagnetic resonance study of Pr_0.6Ca_0.4MnO₃across the charge-ordering transition

Gupta¹,

Joshi²,

Bhat³

et al. 2000

J. Phys.: Condens. Matter

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“…In concentrated systems of transition metal oxides, a strong exchange narrowing effect will usually make the spectra from powdered samples resemble a single Lorentzian lineshape, with some distortion due to the underlying anisotropy [30,31]. In practice, it is usual in these situations to analyze the spin dynamics, as expressed by ∆H, in terms of a single Lorentzian fitting, or in terms of the more crude peak-to-peak distance [32][33][34]. Here, we first follow the former phenomenological approach and then we briefly compare these results with those from a more accurate analysis using the powder profile fitting .…”

Section: Electron Spin Resonancementioning

confidence: 99%

Magnetic dimers and trimers in the disorderedS=32spin systemBaTi1/2Mn1/

Garcia¹,

Kaneko

Granado

et al. 2015

Phys. Rev. B

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We report a structural/magnetic investigation by X-ray absorption spectroscopy (XAS), neutron diffraction, dc-susceptibility (χ dc ) and electron spin resonance (ESR) of the 12R-type perovskite BaTi 1/2 Mn 1/2 O3. Our structural analysis by neutron diffraction supports the existence of structural trimers with chemically disordered occupancy of Mn 4+ and Ti 4+ ions, with the valence of the Mn ions confirmed by the XAS measurements. The magnetic properties are explored by combining dc-susceptibility and X-band (9.4 GHz) electron spin resonance, both in the temperature interval of 2 ≤ T ≤ 1000 K. A scenario is presented under which the magnetism is explained by considering magnetic dimers and trimers, with exchange constants Ja/kB = 200(2) K and J b /kB = 130(10) K, and orphan spins. Thus, BaTi 1/2 Mn 1/2 O3 is proposed as a rare case of an intrinsically disordered S = 3/2 spin gap system with a frustrated ground state.

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“…This variation accompanies the dramatic changes in the electrical conductivity. [18], above ≈ 250 K. Below this temperature a CO process installs [7,14] that frustrate the incipient FM ordering. As a consequence, the magnetization stops to increase and AFM ordering is finally observed with a weak-FM component [7].…”

Section: +mentioning

confidence: 99%

High temperature susceptibility in electron doped Ca_1 xY_xMnO₃: double exchange versus superexchange

Aliaga

Causa

Tovar

et al. 2002

J. Phys.: Condens. Matter

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Abstract. We present a study of the magnetic properties of the electron doped manganites Ca 1-x Y x MnO 3 (for 0 ≤ x ≤ 0.25) in the paramagnetic regime. For the less doped samples (x ≤ 0.1) the magnetic susceptibility, χ(T), follows a Curie-Weiss (CW) law only for T > 450 K and, below this temperature, χ -1 (T) shows a ferrimagnetic-like curvature. We approached the discussion of these results in terms of a simple mean-field model where double exchange, approximated by a ferromagnetic Heisenberg-like interaction between Mn 3+ and Mn 4+ ions, competes with classical superexchange. For higher levels of doping (x ≥ 0.15), the CW behaviour is observed down to the magnetic ordering temperature (T mo ) and a better description of χ(T) was obtained by assuming full delocalization of the e g electrons. In order to explore the degree of delocalization as a function of T and x, we analyzed the problem through Montecarlo simulations. Within this picture we found that at high T the electrons doped are completely delocalized but, when T mo is approached, they form magnetic polarons of large spin that cause the observed curvature in χ -1 (T) for x ≤ 0. IntroductionManganites, responding to the formula B 1-x A x MnO 3 (with B = divalent alkaline earth and A = trivalent rare earth), have prompted a burst of research activity in the last decade, as they enclosed not only very rich physics but also interest in technological applications. The dynamics of these systems is mainly governed by the Mn ions, whose average valence changes with x between 4+ and 3+. The Mn 4+ ions have noncompensated spins in t 2g 3 configuration that give rise to localized S = 3/2 spins. On the other hand, the Mn 3+ ions have an extra e g electron (with s = ½), that couples ferromagnetically (FM) to the t 2g spins. The e g electrons tend to be itinerant and lower their kinetic energy by polarizing with FM character the localized t 2g spins. This process is known [1] as double exchange (DE) and in these materials competes with the classical superexchange (SE) interaction between Mn ions.In Ca 1-x La x MnO 3 were the whole series, from x = 0 to x = 1, can be obtained with the perovskite structure, the behaviour in the electron and hole doping regions were found different. The parent compounds are indeed quite different: while LaMnO 3 , a Jahn-Teller system, displays A-type [2] antiferromagnetism, where ferromagnetic (FM) planes order antiferromagnetically (AFM), the non Jahn-Teller CaMnO 3 is a G-type antiferromagnet, where each magnetic moment orders AFM with his nearest neighbours [2]. Most studies have been performed on hole doped compounds where ferromagnetism and colossal magnetoresistance (CMR) were found. In the range of electron doping, transport and magnetization studies on Ca 1-x La x MnO 3 showed that a complete FM state is never reached and different models were discussed in order to explain the magnetic properties at low temperatures [3,4]. These studies showed that in this region of doping new and very interesting phenomena appear as a conseq...

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High-temperature spin dynamics in CMR manganites: ESR and magnetization

Cited by 255 publications

References 22 publications

An electron paramagnetic resonance study of Pr_0.6Ca_0.4MnO₃across the charge-ordering transition

An electron paramagnetic resonance study of Pr_0.6Ca_0.4MnO₃across the charge-ordering transition

Magnetic dimers and trimers in the disorderedS=32spin systemBaTi1/2Mn1/

High temperature susceptibility in electron doped Ca_1 xY_xMnO₃: double exchange versus superexchange

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High-temperature spin dynamics in CMR manganites: ESR and magnetization

Cited by 255 publications

References 22 publications

An electron paramagnetic resonance study of Pr0.6Ca0.4MnO3across the charge-ordering transition

An electron paramagnetic resonance study of Pr0.6Ca0.4MnO3across the charge-ordering transition

Magnetic dimers and trimers in the disorderedS=32spin systemBaTi1/2Mn1/

High temperature susceptibility in electron doped Ca1 xYxMnO3: double exchange versus superexchange

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An electron paramagnetic resonance study of Pr_0.6Ca_0.4MnO₃across the charge-ordering transition

An electron paramagnetic resonance study of Pr_0.6Ca_0.4MnO₃across the charge-ordering transition

High temperature susceptibility in electron doped Ca_1 xY_xMnO₃: double exchange versus superexchange