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Title: Dual Nature of Improper Ferroelectricity in a Magnetoelectric Multiferroic

Abstract

Using first-principles calculations, we study the microscopic origin of ferroelectricity (FE) induced by magnetic order in the orthorhombic HoMnO3. We obtain the largest ferroelectric polarization observed in the whole class of improper magnetic ferroelectrics to date. We find that the two proposed mechanisms for FE in multiferroics, lattice and electronic based, are simultaneously active in this compound: a large portion of the ferroelectric polarization arises due to quantum-mechanical effects of electron orbital polarization, in addition to the conventional polar atomic displacements. An interesting mechanism for switching the magnetoelectric domains by an electric field via a 180 coherent rotation of Mn spins is also proposed.

Authors:
 [1];  [1];  [2];  [3];  [3]
  1. CNR-INFM, L-Aquila, Italy
  2. Uppsala University, Uppsala, Sweden
  3. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
961780
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 99
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ATOMIC DISPLACEMENTS; ELECTRIC FIELDS; ELECTRONS; FERROELECTRIC MATERIALS; POLARIZATION; ROTATION; SPIN

Citation Formats

Picozzi, S., Yamauchi, K., Sanyal, B., Sergienko, Ivan A, and Dagotto, Elbio R. Dual Nature of Improper Ferroelectricity in a Magnetoelectric Multiferroic. United States: N. p., 2007. Web. doi:10.1103/PhysRevLett.99.227201.
Picozzi, S., Yamauchi, K., Sanyal, B., Sergienko, Ivan A, & Dagotto, Elbio R. Dual Nature of Improper Ferroelectricity in a Magnetoelectric Multiferroic. United States. doi:10.1103/PhysRevLett.99.227201.
Picozzi, S., Yamauchi, K., Sanyal, B., Sergienko, Ivan A, and Dagotto, Elbio R. Mon . "Dual Nature of Improper Ferroelectricity in a Magnetoelectric Multiferroic". United States. doi:10.1103/PhysRevLett.99.227201.
@article{osti_961780,
title = {Dual Nature of Improper Ferroelectricity in a Magnetoelectric Multiferroic},
author = {Picozzi, S. and Yamauchi, K. and Sanyal, B. and Sergienko, Ivan A and Dagotto, Elbio R},
abstractNote = {Using first-principles calculations, we study the microscopic origin of ferroelectricity (FE) induced by magnetic order in the orthorhombic HoMnO3. We obtain the largest ferroelectric polarization observed in the whole class of improper magnetic ferroelectrics to date. We find that the two proposed mechanisms for FE in multiferroics, lattice and electronic based, are simultaneously active in this compound: a large portion of the ferroelectric polarization arises due to quantum-mechanical effects of electron orbital polarization, in addition to the conventional polar atomic displacements. An interesting mechanism for switching the magnetoelectric domains by an electric field via a 180 coherent rotation of Mn spins is also proposed.},
doi = {10.1103/PhysRevLett.99.227201},
journal = {Physical Review Letters},
number = ,
volume = 99,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Two microscopic mechanisms helping us to understand the multiferroic behavior of distorted rare-earth manganites are here briefly reviewed. The original work was carried out by means of Hamiltonian modeling and first-principles density functional simulations. Our first topic concerns the link between the Dzyaloshinskii Moriya interaction and ferroelectricity in incommensurate magnets. We argue that the Dzyaloshinskii Moriya interaction may play a key role since (i) it induces ferroelectric displacements of oxygen atoms and (ii) it favors the stabilization of a helical magnetic structure at low temperatures. Our second topic concerns the prediction, based on Landau theory, that the symmetry of themore » zigzag spin chains in the AFM-E (E-type antiferromagnetic) orthorhombic manganites (such as HoMnO3) allows a finite polarization along the c axis. The microscopic mechanism at the basis of ferroelectricity is interpreted through a gain in band energy of the eg electrons within the orbitally degenerate double-exchange model. Related Monte Carlo simulations have confirmed that the polarization can be much higher than what is observed in spiral magnetic phases. Density functional calculations performed on orthorhombic HoMnO3 quantitatively confirm a magnetically induced ferroelectric polarization up to 6 C cm 2, the largest reported so far for improper magnetic ferroelectrics. We find in HoMnO3, in addition to the conventional displacement mechanism, a sizable contribution arising from the purely electronic effect of orbital polarization. The relatively large ferroelectric polarization, present even with centrosymmetric atomic positions, is a clear sign of a magnetism-induced electronic mechanism at play, which is also confirmed by the large displacements of the Wannier function centers with respect to the corresponding ions in AFM-E HoMnO3. The final polarization is shown to be the result of competing effects, as shown by the opposite signs of the eg and t2g contributions to the ferroelectric polarization.« less
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  • We report the relationship between epitaxial strain and the crystallographic orientation of the in-phase rotation axis and A-site displacements in Pbnm-type perovskite films. Synchrotron diffraction measurements of EuFeO3 films under strain states ranging from 2% compressive to 0.9% tensile on cubic or rhombohedral substrates exhibit a combination of a(-)a(+)c(-) and a(+)a(-)c(-) rotational patterns. We compare the EuFeO3 behavior with previously reported experimental and theoretical work on strained Pbnm-type films on nonorthorhombic substrates, as well as additional measurements from LaGaO3, LaFeO3, and Eu0.7Sr0.3MnO3 films on SrTiO3. Compiling the results from various material systems reveals a general strain dependence in which compressivemore » strain strongly favors a(-)a(+)c(-) and a(+)a(-)c(-) rotation patterns and tensile strain weakly favors a(-)a(-)c(+) structures. In contrast, EuFeO3 films grown on Pbnm-type GdScO3 under 2.3% tensile strain take on a uniform a(-)a(+)c(-) rotation pattern imprinted from the substrate, despite strain considerations that favor the a(-)a(-)c(+) pattern. These results point to the use of substrate imprinting as a more robust route than strain for tuning the crystallographic orientations of the octahedral rotations and A-site displacements needed to realize rotation-induced hybrid improper ferroelectricity in oxide heterostructures.« less
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