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.

P. Murugavel

Department Of Physics

J. Magesh

Antiferromagnetic transition

DIELECTRIC TRANSITION

Double peak

Lattice strain

Magnetoelectric couplings

Spin reorientation

Strong enhancement

Structural distortions

Manganese

Manganese oxide

Antiferromagnetism

Fulltext

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IIT Madras

Strong enhancement of magnetoelectric coupling in Dy3+ doped HoMnO3

Applied Physics Letters

The evolution of various magnetic ordering has been studied for the orthorhombic perovskite GdMn1-xFexO3 (0 x 0.7) system to obtain its comprehensive magnetic phase diagram. We observed that the substitution of Fe in GdMnO3 increases the antiferromagnetic Neel temperature (T N) from 40 K to above 400 K and importantly induces a spin-reorientation transition (T SR) for x 0.4. These transitions are close to room temperature at x = 0.5 and then gradually separated at a higher x value. The static orbital ordering induced by the Jahn-Teller distortion seems to play an important role in changing the T N. The variations of spin-reorientation ordering along with the competition between the magnetic orderings as a function of the composition were discussed with respect to antisymmetric exchange interactions and Mn3+ single-ion anisotropy in detail. In addition, the correlation between structural and magnetic properties suggests that the subtle structural change at composition x = 0.4 may affect the magnetic ordering. The observed tunable T SR and T N in GdMn1-xFexO3 could add a practical value for these compositions in fields like spintronics and sensors. © 2017 IOP Publishing Ltd.

Journal of Physics Condensed Matter

Tailoring of magnetic orderings in Fe substituted GdMnO3 bulk samples towards room temperature

In this paper, the magnetoelectric coupling and ferroelectric ordering of the orthorhombic Dy1-xHoxMnO3 (x=0 and 0.1) are studied from the magnetodielectric response of the polycrystalline samples. The dielectric study on the DyMnO3 reveals ferroelectric transition at 18K along with an addition transition at 12K. We suggest that the transition at 12K could have originated from the polarization flop rather than being the rare earth magnetic ordering. The magnetodielectric study reveals a magnetoelectric coupling strength of 10%, which is stronger by two orders of magnitude in comparison to the hexagonal manganites. Surprisingly, the Ho3+ substitution in DyMnO3 suppresses the magnetoelectric coupling strength via the suppression of the spiral magnetic ordering. In addition, it also reduces the antiferromagnetic ordering and ferroelectric ordering temperatures. Overall, the studies show that the rare earth plays an important role in the magnetoelectric coupling strength through the modulation of spiral magnetic structure. © 2015 AIP Publishing LLC.

Journal of Applied Physics

Ferroelectric ordering and magnetoelectric effect of pristine and Ho-doped orthorhombic DyMnO3 by dielectric studies

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.

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

We fabricated epitaxial (1-x)BiFeO3-xBaTiO3 (x = 0.1-0.7) solid solution films on niobium doped SrTiO3(001) substrate. The x-ray diffraction analysis of the films indicates compressively strained growth for the composition x&lt;0.3 and strain relaxed growth for the composition x≥0.3. Correspondingly, the films showed a structural change from a rhombohedral (or modified monoclinic MA) phase to a tetragonal phase near the composition x∼0.3. Interestingly the ferroelectric measurements showed a distinct difference between the compositions, with the boundary at x∼0.3, above which the films remain in a highly resistive state. The magnetic measurements revealed a weak ferromagnetic signature for the films of composition x≤0.5. © 2008 IOP Publishing Ltd.

Structure and ferroelectric properties of epitaxial (1-x)BiFeO 3-xBaTiO3 solid solution films

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.

Journal	Applied Physics Letters
ISSN	00036951
Open Access	No