Colossal Magnetoresistance in Manganites as a Multicritical Phenomenon

Murakami, Shuichi; Nagaosa, Naoto

doi:10.1103/physrevlett.90.197201

Cited by 70 publications

(18 citation statements)

References 32 publications

(47 reference statements)

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“…1) In addition to the external field, quenched disorder arising from the local lattice distortion and/or doped impurities can also significantly modify the electronic structure in the bicritical region. [2][3][4][5][6][7] A first-order phase transition line separating the two phases completely disappears and instead phase-separated or mixed glassy states on various lengthand time-scales are generated depending on the magnitude of the randomness. Concerning the phase separation caused by strong disorder, effects of impurity doping onto Mn sites have been intensively investigated so far.…”

Section: Introductionmentioning

confidence: 99%

Dopant-Dependent Impact of Mn-Site Doping on Critical-State Manganites R_0.6Sr_0.4MnO₃ (R=La, Nd, Sm, and Gd)

et al. 2008

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Versatile features of impurity doping effects on perovskite manganites, R 0:6 Sr 0:4 MnO 3 , have been investigated by varying the doping species as well as the R-dependent one-electron bandwidth in the single-crystalline specimens. In ferromagnetic-metallic (FM) manganites (R ¼ La, Nd, and Sm), a few percent of Fe substitution dramatically decreases the ferromagnetic transition temperature, leading to a spin glass insulating (SGI) phase for each R species. There, the correlation of charge-orbital ordering in competition with metallic ferromagnetism is effectively induced, which has been observed as an evolution of diffuse electron scattering even in the R ¼ La system with the largest bandwidth. Such a marked impact of Fe doping, widely observed in a variety of FM manganites, virtually results in the reduction in the bandwidth for the system in the critical region near the SGI phase. We have also found a contrastive impact of Cr (or Ru) doping on a SGI manganite (R ¼ Gd). For these dopants, the impurityinduced ferromagnetic magnetization is observed at low temperatures as a consequence of the collapse of the inherent short-range charge-orbital ordering, whereas Fe doping gives only a minimal influence. Thus, the opposite nature of Fe and Cr doping tends to generally hold for bicritical-state manganites with various bandwidths and phase correlation lengths. This may stem from the difference in magnitude of the antiferromagnetic interactions between the Fe-Fe and Cr-Cr couplings.

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Section: Introductionmentioning

confidence: 99%

Dopant-Dependent Impact of Mn-Site Doping on Critical-State Manganites R_0.6Sr_0.4MnO₃ (R=La, Nd, Sm, and Gd)

et al. 2008

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“…x MnO 3 (A ¼ La, Pr, Nd, Sm, Eu, A 0 ¼ Ca, Sr, Ba), are actively synthesized and investigated in order to understand their structural behavior, magnetic properties, and charge or orbital ordering which are often coupled, leading to complex physical properties [1][2][3][4]. Depending on the Asite composition, the manganites can exhibit doubleexchange or superexchange interactions between adjacent Mn 3þ and Mn 4þ cations, leading to a variety of magnetic states including nearly half-metallic ferromagnetism, multiple antiferromagnetic spin structures, spin-glass behavior, and canted antiferromagnetism [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Strain Effects in Narrow-Bandwidth Manganites: The Case of EpitaxialEu0.7Sr0.3MnO3Thin Films

2014

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We have investigated the strain-dependent magnetic properties of epitaxial narrow-bandwidth manganite, Eu 0.7 Sr 0.3 MnO 3 (ESMO), thin films on various substrates traversing from compressive (−2.4%) to tensile (þ1.5%) strain. The stoichiometry and crystalline quality of the films were confirmed with diffraction and spectroscopic-based characterization. Using field-and temperature-dependent magnetometry, we find that the epitaxial strain acts to suppress the ferromagnetic state, although films under compressive strain retain a greater propensity for ferromagnetic behavior. However, temperature-dependent resistivity reveals that ESMO thin films exhibit a ferromagnetic insulating state in contrast to widebandwidth La 0.7 Sr 0.3 MnO 3 films under a comparable strain. The combination of a highly strain-dependent ferromagnetic state and robust insulating behavior may offer novel applications in spin filtering, sensing, or electronics.

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“…Pinning these details down and then understanding their implications will certainly be an area of intense study in the near future. It is becoming increasingly clear that some of the most dramatic responses in modern materials occur in systems in which multiple phases or orders with similar energy scales compete with each other [22][23][24]28 . It is then natural that in at least some of these systems spatial heterogeneities will occur, and small perturbations can cause drastic macroscopic alterations to the physical properties or even new types of 'emergent' behaviour.…”

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confidence: 99%

A local metallic state in globally insulating La1.24Sr1.76Mn2O7 well above the metal–insulator transition

et al. 2007

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The distinction between metals, semiconductors and insulators depends on the behaviour of the electrons nearest the Fermi level E F , which separates the occupied from the unoccupied electron energy levels. For a metal, E F lies in the middle of a band of electronic states, whereas E F in insulators and semiconductors lies in the gap between states. The temperatureinduced transition from a metallic to an insulating state in a solid is generally connected to a vanishing of the low-energy electronic excitations 1 . Here we show the first direct evidence of a counter-example, in which a significant electronic density of states at the Fermi energy exists in the insulating regime. In particular, angle-resolved photoemission data from the colossal magnetoresistive oxide La 1.24 Sr 1.76 Mn 2 O 7 show clear Fermi-edge steps, both below the metal-insulator transition temperature T C , when the sample is globally metallic, and above T C , when it is globally insulating. Further, small amounts of metallic spectral weight survive up to temperatures more than twice T C . Such behaviour may also have close ties to a variety of exotic phenomena in correlated electron systems, including the pseudogap temperature in underdoped cuprates 2 .As shown in Fig. 1a, the colossal magnetoresistive (CMR) oxide La 2−2x Sr 1+2x Mn 2 O 7 (x = 0.36,0.38) shows a metal-insulator transition at a T C just below 130 K, at which point the system also switches from being a ferromagnet (low temperature T) to a paramagnet (high T) 3 . We carried out angle-resolved photoemission spectroscopy (ARPES) experiments on cleaved single crystals of these materials, with an experimental arrangement as described elsewhere 4 . ARPES is an ideal experimental probe of the electronic structure because it gives the momentum-resolved single-particle excitation spectrum. As discussed in ref. 4, the x = 0.36, 0.38 compounds studied here do not contain the lowenergy pseudogap of the x = 0.4 samples 5-8 (see the Methods section for more details on this, the possible issue of surface sensitivity of ARPES and of possible intergrowths at the surface). The much larger metallic spectral weight of these nonpseudogapped compounds also allows us to study the electronic behaviour in greater detail. Although we find only minimal differences between the x = 0.36 and x = 0.38 compounds, all ARPES spectra shown here are from x = 0.38 samples. Figure 1b shows a large-energy-scale experimental picture of a low-temperature d x 2 −y 2 symmetry band taken along the blue cut near the zone boundary, as shown in the inset. We are able to get clean data by isolating the various bilayer-split bands using different photon energies, as described in ref. 4. In particular, in this paper we show only data from the antibonding bilayer-split band, which has Fermi crossings at k x = ±0.17π/a, k y = 0.9π/a, corresponding to the solid Fermi surface of the inset of Fig. 1b. The energy-distribution curves (EDCs) at the Fermi wavevector k F (indicated by the red line in Fig. 1b) taken at a series of temper...

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Colossal Magnetoresistance in Manganites as a Multicritical Phenomenon

Cited by 70 publications

References 32 publications

Dopant-Dependent Impact of Mn-Site Doping on Critical-State Manganites R_0.6Sr_0.4MnO₃ (R=La, Nd, Sm, and Gd)

Dopant-Dependent Impact of Mn-Site Doping on Critical-State Manganites R_0.6Sr_0.4MnO₃ (R=La, Nd, Sm, and Gd)

Strain Effects in Narrow-Bandwidth Manganites: The Case of EpitaxialEu0.7Sr0.3MnO3Thin Films

A local metallic state in globally insulating La1.24Sr1.76Mn2O7 well above the metal–insulator transition

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Colossal Magnetoresistance in Manganites as a Multicritical Phenomenon

Cited by 70 publications

References 32 publications

Dopant-Dependent Impact of Mn-Site Doping on Critical-State Manganites R0.6Sr0.4MnO3 (R=La, Nd, Sm, and Gd)

Dopant-Dependent Impact of Mn-Site Doping on Critical-State Manganites R0.6Sr0.4MnO3 (R=La, Nd, Sm, and Gd)

Strain Effects in Narrow-Bandwidth Manganites: The Case of EpitaxialEu0.7Sr0.3MnO3Thin Films

A local metallic state in globally insulating La1.24Sr1.76Mn2O7 well above the metal–insulator transition

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Dopant-Dependent Impact of Mn-Site Doping on Critical-State Manganites R_0.6Sr_0.4MnO₃ (R=La, Nd, Sm, and Gd)

Dopant-Dependent Impact of Mn-Site Doping on Critical-State Manganites R_0.6Sr_0.4MnO₃ (R=La, Nd, Sm, and Gd)