The authors investigated the magnetic and ferroelectric properties of hexagonally grown HoMn O3 thin films. The magnetic measurements revealed bulklike magnetic phase transitions with an additional spin-glass-like behavior feature below the Náel temperature. The ferroelectricity in the films was distinctly different from the suggested bulk behavior. Below 40 K, the HoMn O3 films showed typical ferroelectric character: their remnant polarization and coercive field values at 20 K were 3.7 μC cm2 and 0.69 MVcm. Above 40 K, however, the films exhibited an unusual antiferroelectriclike behavior, with more pronounced features appearing at higher temperatures. These intriguing physical properties make HoMn O3 films a potential candidate material for numerous future applications. © 2007 American Institute of Physics.

P. Murugavel

Department Of Physics

Antiferroelectricity

Coercive force

Ferroelectricity

Phase Transitions

Spin glass

BULK BEHAVIOR

COERCIVE FIELDS

magnetic phase transitions

REMNANT POLARIZATION

Magnetic thin films

Fulltext

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IIT Madras

Physical properties of multiferroic hexagonal HoMnO3 thin films

Applied Physics Letters

This paper investigates the magnetic properties of Ho1-xDyxMnO3 by considering the inter-planar Mn3+-O-O-Mn3+ interaction. The theoretical analysis shows that the asymmetric in-plane exchange interaction couples the in-plane and inter-planar Mn3+ spin structures via asymmetry parameter δ. This leads to the existence of both the in-plane and inter-planar ordering, which in turn restricted the allowed magnetic space groups to Γ1 and Γ4. The experimental studies confirmed the concomitant nature of the in-plane and the inter-planar ordering at TN, TSR, and T2. It also showed that the magnetic phase diagram is dominated by the allowed magnetic structures Γ1 and Γ4. Furthermore, an effort is made to resolve the inconsistency regarding the TSR (32 or 40 K). The studies revealed that the antiferromagnetic inter-planar interaction is switched to the ferromagnetic interaction (40 K) upon cooling, which in turn drives the spin reorientation at 32 K. The Mn3+ spin structure is seen to be coupled to rare earth sub-lattice through the modulation of the inter-planar interaction. © 2015 AIP Publishing LLC.

Journal of Applied Physics

A study of magnetic ordering in multiferroic hexagonal Ho1-xDyxMnO3

The role of rare earth ion R3+ in spin reorientation and magneto dielectric response is investigated by substitution of non-magnetic smaller ionic radii Lu3+ in multiferroic hexagonal HoMnO3. The XRD analysis suggests that the dopant may preferably goes to C3V site up to 1/3rd of the composition in order to reduce the lattice distortion. We suggest that the R3+ ion at C3 site could play a strong role in spin reorientation than the C3V site. The observation of TSR even in LuMnO3 precludes the role of rare earth magnetic moment in driving the spin reorientation. Surprisingly, the magneto dielectric response of HoMnO3 is dominated by the rare earth RO 8 dipoles. The oppositely oriented RO8 dipole at the C3V and C3 determines the magneto dielectric response in various magnetic phases reaffirming the site specific substitution. Thus, site specific doping could be a way to enhance the magnetoelectric coupling strength. © 2013 AIP Publishing LLC.

Role of rare earth on the Mn3+ spin reorientation in multiferroic Ho1-xLuxMnO3

The magnetodielectric studies on hexagonal Ho1- xDyxMnO3 reveal an overall enhancement of magnetoelectric coupling upon Dy3 substitution. However, the magnitude of the enhancement is varied with doping level x. Magnetodielectric response is larger for x 0.1 and it started decreasing with further increase in x. We suggest that the specific site (C3V site) substitution of higher ionic radii Dy3 in the structure could play a key role in defining magnetoelectric coupling strength through structural distortion. The evolution of c/a ratio which is a measure of distortion in the hexagonal lattice agrees well with the observed percentage change in the dielectric constant which in turn substantiates the role of lattice distortion on the enhancement in magnetodielectric effect. © 2012 American Institute of Physics.

Study of magnetodielectric effect in hexagonal Ho1-xDy xMnO3

The magnetoelectric effect in Ho 0.9Dy 0.1MnO 3 is found 31 times stronger than HoMnO 3 which could be due to strong lattice frustration arises out of the structural distortion on doping. The T N observed from magnetic measurement reveals a double peak corresponding to the in-plane and inter-planar ordering leading to assignment of Γ 4 structure. The antiferromagnetic transition at T N indeed drives dielectric transition mediated by the lattice strain whereas at the T SR, lattice strain drives the spin reorientation of Mn 3+. In contrary to the long held belief, the magnetic structure changes from Γ 4 to Γ 1 at T SR instead of Γ 4 to Γ 3. © 2012 American Institute of Physics.

Strong enhancement of magnetoelectric coupling in Dy 3+ doped HoMnO 3

The epitaxial growth of the artificial hexagonal GdMnO3 phase was investigated on substrates with hexagonal symmetries. The GdMnO3 thin films grown on Pt(1 1 1)/Al2O3(0 0 0 1) substrates showed a mixed state of a dominant hexagonal phase and small additional orthorhombic phases, which were stable in bulk. In this study, high oxygen partial pressures during film deposition were found to help to fabricate GdMnO3 thin films in the dominant hexagonal phase. Also, the growth behavior of the small additional orthorhombic GdMnO3 phases was studied by X-ray diffraction (XRD) measurements with a synchrotron radiation X-ray source. This study confirmed that even the orthorhombic GdMnO3 phases prefer specific orientations on the substrates with an in-plane hexagonal symmetry. © 2007 Elsevier B.V. All rights reserved.

Journal of Crystal Growth

Growth behavior of artificial hexagonal GdMnO3 thin films

Journal of the Korean Ceramic Society

Measured Polarization Hysteresis and Predicted Reference Remnant Polarization and Strains of Ferroelectric Ceramics at Various Electric Field Loading Rates and Temperatures

Multiferroic properties of epitaxially stabilized hexagonal DyMnO3 thin films

Physical Review Letters

Polarization Switching Dynamics Governed by the Thermodynamic Nucleation Process in Ultrathin Ferroelectric Films

Advanced Materials

Epitaxial Stabilization of a New Multiferroic Hexagonal Phase of TbMnO3 Thin Films

Coercive fields in ultrathin BaTiO3 capacitors

Physical properties of multiferroic hexagonal HoMn O3 thin films

Journal	Applied Physics Letters
ISSN	00036951
Open Access	No