1
|
Grain-Size-Induced Collapse of Variable Range Hopping and Promotion of Ferromagnetism in Manganite La0.5Ca0.5MnO3. CRYSTALS 2022. [DOI: 10.3390/cryst12050724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Among transition metal oxides, manganites have attracted significant attention because of colossal magnetoresistance (CMR)—a magnetic field-induced metal–insulator transition close to the Curie temperature. CMR is closely related to the ferromagnetic (FM) metallic phase which strongly competes with the antiferromagnetic (AFM) charge ordered (CO) phase, where conducting electrons localize and create a long range order giving rise to insulator-like behavior. One of the major open questions in manganites is the exact origin of this insulating behavior. Here we report a dc resistivity and magnetization study on manganite La1−xCaxMnO3 ceramic samples with different grain size, at the very boundary between CO/AFM insulating and FM metallic phases x=0.5. Clear signatures of variable range hopping (VRH) are discerned in resistivity, implying the disorder-induced (Anderson) localization of conducting electrons. A significant increase of disorder associated with the reduction in grain size, however, pushes the system in the opposite direction from the Anderson localization scenario, resulting in a drastic decrease of resistivity, collapse of the VRH, suppression of the CO/AFM phase and growth of an FM contribution. These contradictory results are interpreted within the standard core-shell model and recent theories of Anderson localization of interacting particles.
Collapse
|
2
|
Sinclair R, Cao HB, Garlea VO, Lee M, Choi ES, Dun ZL, Dong S, Dagotto E, Zhou HD. Canted magnetic ground state of quarter-doped manganites R 0.75Ca 0.25MnO 3 (R = Y, Tb, Dy, Ho, and Er). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:065802. [PMID: 28002058 DOI: 10.1088/1361-648x/aa4de1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Polycrystalline samples of the quarter-doped manganites R 0.75Ca0.25MnO3 (R = Y, Tb, Dy, Ho, and Er) were studied by x-ray diffraction and AC/DC susceptibility measurements. All five samples are orthorhombic and exhibit similar magnetic properties: enhanced ferromagnetism below T 1 (∼80 K) and a spin glass (SG) state below T SG (∼30 K). With increasing R 3+ ionic size, both T 1 and T SG generally increase. The single crystal neutron diffraction results on Tb0.75Ca0.25MnO3 revealed that the SG state is mainly composed of a short-range ordered version of a novel canted (i.e. noncollinear) antiferromagnetic spin state. Furthermore, calculations based on the double exchange model for quarter-doped manganites reveal that this new magnetic phase provides a transition state between the ferromagnetic state and the theoretically predicted spin-orthogonal stripe phase.
Collapse
Affiliation(s)
- R Sinclair
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
3
|
Localization of electrons due to orbitally ordered bi-stripes in the bilayer manganite La(2-2x)Sr(1+2x)Mn2O7 (x ~ 0.59). Proc Natl Acad Sci U S A 2011; 108:11799-803. [PMID: 21715662 DOI: 10.1073/pnas.1018604108] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Electronic phases with stripe patterns have been intensively investigated for their vital roles in unique properties of correlated electronic materials. How these real-space patterns affect the conductivity and other properties of materials (which are usually described in momentum space) is one of the major challenges of modern condensed matter physics. By studying the electronic structure of La(2-2x)Sr(1+2x)Mn(2)O(7) (x ∼ 0.59) and in combination with earlier scattering measurements, we demonstrate the variation of electronic properties accompanying the melting of so-called bi-stripes in this material. The static bi-stripes can strongly localize the electrons in the insulating phase above T(c) ∼ 160 K, while the fraction of mobile electrons grows, coexisting with a significant portion of localized electrons when the static bi-stripes melt below T(c). The presence of localized electrons below T(c) suggests that the melting bi-stripes exist as a disordered or fluctuating counterpart. From static to melting, the bi-stripes act as an atomic-scale electronic valve, leading to a "colossal" metal-insulator transition in this material.
Collapse
|
4
|
Chae SC, Horibe Y, Jeong DY, Rodan S, Lee N, Cheong SW. Self-organization, condensation, and annihilation of topological vortices and antivortices in a multiferroic. Proc Natl Acad Sci U S A 2010; 107:21366-70. [PMID: 21115846 PMCID: PMC3003016 DOI: 10.1073/pnas.1011380107] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The interaction among topological defects can induce novel phenomena such as disclination pairs in liquid crystals and superconducting vortex lattices. Nanoscale topological vortices with swirling ferroelectric, magnetic, and structural antiphase relationships were found in multiferroic h-YMnO(3). Herein, we report the discovery of intriguing, but seemingly irregular configurations of a zoo of topological vortices and antivortices. These configurations can be neatly analyzed in terms of graph theory and reflect the nature of self-organized criticality in complexity phenomena. External stimuli such as chemistry-driven or electric poling can induce the condensation and eventual annihilation of topological vortex-antivortex pairs.
Collapse
Affiliation(s)
- S. C. Chae
- Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854; and
| | - Y. Horibe
- Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854; and
| | - D. Y. Jeong
- Department of Mathematics, Soongsil University, Seoul 156-743, Korea
| | - S. Rodan
- Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854; and
| | - N. Lee
- Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854; and
| | - S.-W. Cheong
- Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854; and
| |
Collapse
|
5
|
Brey L. Continuous charge modulated diagonal phase in manganites. PHYSICAL REVIEW LETTERS 2004; 92:127202. [PMID: 15089701 DOI: 10.1103/physrevlett.92.127202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2003] [Indexed: 05/24/2023]
Abstract
We present a novel ground state that explains the continuous charge modulated diagonal order recently observed in manganese oxides, at hole concentrations x larger than one-half. In this diagonal phase the charge is modulated with a predominant Fourier component inversely proportional to 1-x. Magnetically this state consists of antiferromagnetically coupled zigzag chains. For a wide range of physical parameters such as electron-phonon coupling, antiferromagnetic interaction between Mn ions, and on-site Coulomb repulsion, the diagonal phase is the ground state of the system. Also we find that the diagonal modulation of the electron density is only a small fraction of the average charge, a much smaller modulation than the one obtained by distributing Mn+3 and Mn+4 ions. We discuss also the spin and orbital structure properties of this new diagonal phase.
Collapse
Affiliation(s)
- Luis Brey
- Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049 Madrid, Spain
| |
Collapse
|
6
|
Manganites. ACTA ACUST UNITED AC 2004. [DOI: 10.1007/978-3-662-09298-9_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
|
7
|
Solovyev IV. Charge ordering due to magnetic symmetry breaking. PHYSICAL REVIEW LETTERS 2003; 91:177201. [PMID: 14611372 DOI: 10.1103/physrevlett.91.177201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2002] [Indexed: 05/24/2023]
Abstract
It is argued that both transitions observed in 50% doped manganites, at the Néel temperature (T(N)) and the so-called charge ordering temperature (T(CO)), are magnetic. T(N) corresponds to the order-disorder transition, which takes place between ferromagnetic zigzag chains, while the coherent motion of spins within the chains is destroyed only around T(CO). The magnetic structure below T(CO) is highly anisotropic. It is dressed by the lattice distortion and leads to the huge anisotropy of the electronic structure, which explains stability of this state as well as the form of the charge-orbital pattern above T(N). The type of phase transition at T=T(N) is determined by lattice interactions.
Collapse
Affiliation(s)
- I V Solovyev
- Tokura Spin Superstructure Project, ERATO Japan Science and Technology Corporation, National Institute of Advanced Industrial Science and Technology, Central 4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562, Japan.
| |
Collapse
|
8
|
Hotta T, Moraghebi M, Feiguin A, Moreo A, Yunoki S, Dagotto E. Unveiling new magnetic phases of undoped and doped manganites. PHYSICAL REVIEW LETTERS 2003; 90:247203. [PMID: 12857223 DOI: 10.1103/physrevlett.90.247203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2002] [Indexed: 05/24/2023]
Abstract
Novel ground-state spin structures in undoped and lightly doped manganites are investigated based on the orbital-degenerate double-exchange model, via mean-field and numerical techniques. In undoped manganites, a new antiferromagnetic (AFM) state, called the E-type phase, is found adjacent in parameter space to the A-type AFM phase. Its structure is in agreement with recent experimental results. This insulating E-AFM state is also competing with a ferromagnetic metallic phase as well. For doped layered manganites, the phase diagram includes another new AFM phase of the CxE1-x type. Experimental signatures of the new phases are discussed.
Collapse
Affiliation(s)
- Takashi Hotta
- Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195, Japan
| | | | | | | | | | | |
Collapse
|
9
|
|
10
|
Chuang YD, Gromko AD, Dessau DS, Kimura T, Tokura Y. Fermi surface nesting and nanoscale fluctuating charge/orbital ordering in colossal magnetoresistive oxides. Science 2001; 292:1509-13. [PMID: 11326084 DOI: 10.1126/science.1059255] [Citation(s) in RCA: 166] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We used high-resolution angle-resolved photoemission spectroscopy to reveal the Fermi surface and key transport parameters of the metallic state of the layered colossal magnetoresistive oxide La1.2Sr1.8Mn2O7. With these parameters, the calculated in-plane conductivity is nearly one order of magnitude larger than the measured direct current conductivity. This discrepancy can be accounted for by including the pseudogap, which removes at least 90% of the spectral weight at the Fermi energy. Key to the pseudogap and to many other properties are the parallel straight Fermi surface sections, which are highly susceptible to nesting instabilities. These nesting instabilities produce nanoscale fluctuating charge/orbital modulations, which cooperate with Jahn-Teller distortions and compete with the electron itinerancy favored by double exchange.
Collapse
Affiliation(s)
- Y D Chuang
- Department of Physics, University of Colorado, Boulder, CO 80309-0390, USA
| | | | | | | | | |
Collapse
|
11
|
Hotta T, Feiguin A, Dagotto E. Stripes induced by orbital ordering in layered manganites. PHYSICAL REVIEW LETTERS 2001; 86:4922-4925. [PMID: 11384382 DOI: 10.1103/physrevlett.86.4922] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2000] [Indexed: 05/23/2023]
Abstract
Spin-charge-orbital ordered structures in doped layered manganites are investigated using an orbital-degenerate double-exchange model tightly coupled to Jahn-Teller distortions. In the ferromagnetic phase, unexpected diagonal stripes at x = 1/m ( m = integer) are observed, as in recent experiments. These stripes are induced by the orbital degree of freedom, which forms a staggered pattern in the background. A pi shift in the orbital order across stripes is identified, analogous to the pi shift in spin order across stripes in cuprates. At x = 1/4 and 1/3, another nonmagnetic phase with diagonal static charge stripes is stabilized at intermediate values of the t(2g)-spins exchange coupling.
Collapse
Affiliation(s)
- T Hotta
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba 277-8581, Japan
| | | | | |
Collapse
|
12
|
Hotta T, Dagotto E, Koizumi H, Takada Y. Comment on "charge-orbital stripe structure in La1-xCaxMnO3 ( x = 1/2, 2/3)". PHYSICAL REVIEW LETTERS 2001; 86:2478-2479. [PMID: 11289959 DOI: 10.1103/physrevlett.86.2478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2000] [Indexed: 05/23/2023]
Affiliation(s)
- T Hotta
- Institute for Solid State Physics, University of Tokyo, Chiba, Japan
| | | | | | | |
Collapse
|
13
|
Mayr M, Moreo A, Vergés JA, Arispe J, Feiguin A, Dagotto E. Resistivity of Mixed-Phase Manganites. PHYSICAL REVIEW LETTERS 2001; 86:135-138. [PMID: 11136112 DOI: 10.1103/physrevlett.86.135] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2000] [Indexed: 05/23/2023]
Abstract
The resistivity rho(dc) of manganites is studied using a random resistor-network, based on phase separation between metallic and insulating domains. When percolation occurs, both as chemical composition or temperature vary, results in good agreement with experiments are obtained. Similar conclusions are reached using quantum calculations and microscopic considerations. Above the Curie temperature, it is argued that ferromagnetic clusters should exist in Mn oxides. Small magnetic fields induce large rho(dc) changes and a bad-metal state with (disconnected) insulating domains.
Collapse
Affiliation(s)
- M Mayr
- National High Magnetic Field Lab and Department of Physics, Florida State University, Tallahassee, Florida 32306
| | | | | | | | | | | |
Collapse
|
14
|
Moreo A, Mayr M, Feiguin A, Yunoki S, Dagotto E. Giant cluster coexistence in doped manganites and other compounds. PHYSICAL REVIEW LETTERS 2000; 84:5568-5571. [PMID: 10990996 DOI: 10.1103/physrevlett.84.5568] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2000] [Indexed: 05/23/2023]
Abstract
Computational studies of models for manganese oxides show the generation of large coexisting metallic and insulating clusters with equal electronic density, in agreement with the recently discovered micrometer-sized inhomogeneities in manganites. The clusters are induced by disorder on exchange and hopping amplitudes near first-order transitions of the nondisordered strongly coupled system. The random-field Ising model illustrates the qualitative aspects of our results. Percolative characteristics are natural in this context. The conclusions are general and apply to a variety of compounds.
Collapse
Affiliation(s)
- A Moreo
- National High Magnetic Field Lab and Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
| | | | | | | | | |
Collapse
|
15
|
Yunoki S, Hotta T, Dagotto E. Ferromagnetic, A-type, and charge-ordered CE-type states in doped manganites using jahn-teller phonons. PHYSICAL REVIEW LETTERS 2000; 84:3714-3717. [PMID: 11019184 DOI: 10.1103/physrevlett.84.3714] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/1999] [Indexed: 05/23/2023]
Abstract
The two-orbital model for manganites with both noncooperative and cooperative Jahn-Teller phonons is studied at hole density x = 0.5 using Monte Carlo techniques. The phase diagram is obtained by varying the electron-phonon coupling and the t(2g)-spins exchange. The insulating CE-type charge- and orbital-ordered state with the z-axis charge stacking observed in narrow-bandwidth manganites is stabilized in the simulations. Its charge gap Delta(CO) is much larger than the critical temperature k(B)T(CO). Metalliclike A-type and ferromagnetic states are also obtained in the same framework, and the phase boundaries among them have first-order characteristics.
Collapse
Affiliation(s)
- S Yunoki
- National High Magnetic Field Laboratory and Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
| | | | | |
Collapse
|