The correlation between static magnetoelectric coupling and magnetic structure was investigated in $TbMn_{0.98}Fe_{0.02}O_{3}$ with magnetic field up to 8 T and down to 2 K. Single-crystal neutron diffraction experiments reveal a substantial increase in the temperature dependence of the incommensurate modulation wave vector of the antiferromagnetic phase as the magnetic field strength increases. Magnetic field-dependent pyroelectric current measurements revealed significantly higher magnetoelectric coupling at magnetic fields below 4 T than in pure TbMnO3. This is due to the higher sensitivity of the incommensurably modulated cycloid structure to weak magnetic fields. Detailed analysis of our data confirmed that the ferroelectric polarization is induced by inverse Dzyaloshinskii-Moriya interaction for magnetic field strength up to 4 T, but at higher fields a departure from theoretical predictions is ascertained, giving evidence for an additional, as yet misunderstood, contribution to magnetoelectric coupling. It shows that a small 2% substitution of Mn3+ by Fe3+ has a strong impact on the magnetic structure, promoting the destabilization of the incommensurably modulated magnetic cycloidal structure of $TbMnO_{3}$ in a magnetic field above 5 T. We demonstrate that the magnetoelectric coupling magnitude can be tuned through suitable substitutional elements, even at low level, inducing local lattice distortions with different electronic and magnetic properties.
In this work, we report the growth and functional characterizations of multiferroic TbMnO3 thin films grown on Nb-doped SrTiO3 (001) substrates using pulsed laser deposition. By performing detailed magnetic and ferroelectric properties measurements, we demonstrate that the multiferroicity of spin origin known in the bulk crystals can be successfully transferred to TbMnO3 thin films. Meanwhile, anomalous magnetic transition and unusual magnetoelectric coupling related to Tb moments are observed, suggesting a modified magnetic configuration of Tb in the films as compared to the bulk counterpart.…
Magnetoelectric, dielectric and magnetic susceptibility tensors of multiferroic TbMnO3 with cycloidal antiferromagnetic structure in external electric and magnetic fields have been investigated with taking into account dynamics of spin, electro-dipole and acoustic subsystems. All components of tensors depend on values of external electric and magnetic fields. The possibility of control of electrodynamic properties of multiferroic TbMnO3 with cycloidal antiferromagnetic structure by external electric and magnetic fields has been shown. The resonant interaction of spin, electro-dipole, electroma…
A current challenge in the field of magnetoelectric multiferroics is to identify systems that allow a controlled tuning of states displaying distinct magnetoelectric responses. Here we show that the multiferroic ground state of the archetypal multiferroic TbMnO3 is dramatically modified by epitaxial strain. Neutron diffraction reveals that in highly strained films the magnetic order changes from the bulk-like incommensurate bc-cycloidal structure to commensurate magnetic order. Concomitant with the modification of the magnetic ground state, optical second-harmonic generation (SHG) and electric…
We report a comprehensive study of the low-level substitution of Mn$^{3+}$ by Fe$^{3+}$ effect on the static and dynamic magnetoelectric coupling in TbMn$_{1-x}$Fe$_x$O$_3$ ($x=0$, 0.02 and 0.04). The cationic substitution has a large impact on the balance between competitive magnetic interactions and, as a result, on the stabilization of the magnetic structures and ferroelectric phase at low temperatures. Low-lying electromagnon excitation is activated in the cycloidal modulated antiferromagnetic and ferroelectric phase in TbMnO$_3$, while it is observed up to TN in the Fe-substituted compoun…
Magnetoelectric multiferroic composite of two types of multiferroic (Type I and II) consisting BiFeO3 and TbMnO3 is studied for enhanced magnetic and transport properties. A narrower band gap is estimated from the UV-visible absorption spectrum from that of BiFeO3 and TbMnO3. With known value of band gap, the band structure was estimated from the valence band x-ray photoemission spectra (XPS) and ultra violet photoemission spectra (UPS). The valence and conduction band was found at 1.0 eV and 0.45 eV above and below the Fermi level respectively. Thus the insulating behavior of the system is un…
The magnetoelectric coupling, i.e., cross-correlation between electric and magnetic orders, is a very desirable property to combine functionalities of materials for next-generation switchable devices. Multiferroics with spin-driven ferroelectricity presents such a mutual interaction concomitant with magneto- and electro-active excitations called electromagnons. TbMnO3 is a paradigmatic material in which two electromagnons have been observed in the cycloidal magnetic phase. However, their observation in TbMnO3 is restricted to the cycloidal spin phase and magnetic ground states that can support…
We report the effect of Ba and Zr co-substitution on structural, dielectric, magnetic and magnetoelectric properties of BiFeO3 multiferroics. Polycrystalline nanoceramic samples of Bi1- xBaxFe1-yZryO3 have been synthesized by auto-combustion method. Rietveld refinement result of X-ray diffraction data indicate a contraction of unit cell volume with increase in x and y. Field emission scanning electron micrographs show densely populated grains without any voids or defects with well-defined grain boundary and decrease in grain size with increasing x and y. The result of dielectric measurement di…
We report experimental studies on enhancing the magnetoelectric (ME) coupling of Co$_4$Nb$_2$O$_9$ by substitution of non-magnetic metal Mg for Co. A series of single crystal Co$_{4-x}$Mg$_x$Nb$_2$O$_9$ (x=0, 1, 2, 3) with a single-phase corundum-type structure are synthesized by the optical floating zone method, and the good quality and crystallographic orientations of the synthesized samples are confirmed by Laue spots and sharp XRD peaks. Although the Neel temperature ($T_N$) of the Mg substituted crystals are slightly decreased from 27 K for pure Co$_4$Nb$_2$O$_9$ to 19 K and 11 K for Co$_…
Hybrid organometallic systems offer a wide range of functionalities, including magnetoelectric interactions. However, the ability to design on-demand ME coupling remains challenging despite a variety of host-guest configurations and ME phases coexistence possibilities. Here, we report the effect of metal-ion substitution on the magnetic and electric properties in the paramagnetic ferroelectric DMAAS crystals. Doing so we are able to induce and even tune a sign of the ME interactions in the paramagnetic ferroelectric state. Both studied samples with 6.5% and 20% of Cr become paramagnetic, contr…
Few materials undergo cooperative Jahn-Teller (JT) transitions at low temperatures, but zircon-type oxides are one class that includes DyVO$_4$, which transforms from a tetragonal to an orthorhombic structure at around 13.6 K, with a narrow transition temperature range within 0.5 K. Since many rare-earth ions can be accommodated in the structure, there should be ample routes to vary the transition temperature and structural effects of the transition. We have synthesized pure DyVO$_4$ and solid solutions Dy$_{1-x}$Tm$_x$VO$_4$ ($x$ = 0.05, 0.1, 0.15, 0.2, and 0.5) and Dy$_{1-y}$Pr$_y$VO$_4$ ($y…
(Ba/Sr)3NbFe3Si2O14 is a magnetoelectric multiferroic with an incommensurate antiferromagnetic spiral magnetic structure which induces electric polarization at 26 K. The structure, as revealed by x-rays and neutrons, as well as static and dynamic magnetic and dielectric properties of these compounds have been studied down to 6 K under different conditions. Both the compounds have similar crystal structure but with different lattice constants down to 6 K. The Ba-and Sr-compounds exhibit a transition at 26 K and 25 K respectively, as indicated by the specific heat capacity and dc specific magnet…
We show that low field magnetoelectric (ME) properties of helimagnets Ba0.5Sr1.5Zn2(Fe1-xAlx)12O22 can be efficiently tailored by Al-substitution level. As x increases, the critical magnetic field for switching electric polarization is systematically reduced from ~1 T down to ~1 mT, and the ME susceptibility is greatly enhanced to reach a giant value of 2.0 x 10^4 ps/m at an optimum x = 0.08. We find that control of nontrivial orbital moment in the octahedral Fe sites through the Al-substitution is crucial for fine tuning of magnetic anisotropy and obtaining the conspicuously improved ME chara…
The effect of Cr doping with nominal compositions Mn2-xCrxO3 (0 less than equal to x less than equal to 0.10) has been undertaken to investigate its effect on structural, magnetic, dielectric and magnetoelectric properties. The Cr doping transformed the room temperature crystal structure from orthorhombic to cubic symmetry. Similar to alpha-Mn2O3, two magnetic transitions have been observed in the Cr doped samples. The effect of Cr doping is significant on the low temperature transition i.e. the lower magnetic transition shifted towards higher temperature (25 K for pristine to 40 K for x=0.10)…
We have successfully induced multiferroic behavior in the A-type antiferromagnet SmMnO3 by the substitution of Y at the Sm site. A magnetic transition develops at 24 K for Sm1-xYxMnO3 (x=0.4,0.5) which is not present in the parent compound. This transition coincides with the onset of electric order, with an electric polarization measured along the c axis. It is proposed that the effect of Y doping is to bring about a subtle distortion of the MnO6 octahedra, causing a magnetic ordering of the Mn3+ moments similar to that reported for the well studied multiferroic TbMnO3. Following on from our p…
We present a study of the dielectric, structural, and magnetic properties of the multiferroic or linear magnetoelectric substitution series [(NH$_4$)$_{1-x}$K$_x$]$_2$[FeCl$_5$(H$_2$O)]. Pyroelectric currents, magnetic susceptibilities, and thermodynamic properties were examined on large single crystals of the erythrosiderite compounds and detailed magnetic-field versus temperature phase diagrams are derived for three different substitution levels. With increasing potassium concentration the material is tuned from a multiferroic ($x \le 0.06$) to a linear magnetoelectric ($x \ge 0.15$) ground …
We report the occurrence of both \emph{ab} and \emph{bc} cycloidal ordering of Mn-spins at different temperatures and their possible coexistence at low temperatures in the polycrystalline mixed rare-earth compounds, \emph{R}$_{0.5}$Dy$_{0.5}$MnO$_3$ (\emph{R} = Eu and Gd), which exhibit extraordinary magnetoelectric properties. While the polarization of Gd$_{0.5}$Dy$_{0.5}$MnO$_3$ is comparable to TbMnO$_3$, the compound Eu$_{0.5}$Dy$_{0.5}$MnO$_3$ shows high value of polarization. However, both of them show giant magnetic tunability and exhibit large magnetocapacitance whose sign changes acro…
In this work, the potential to exploit Aurivillius higher order composition (n=6) given by Bi4Ti3O12-3BiFeO3 as single phase and high temperature magnetoelectric materials are well explored by elaborately studying the concerned structure and physical properties. Bi4Ti3O12-3Bi1-xLaxFeO3 (x=0, 0.01, 0.05, 0.1, 0.2) was synthesized via solid-state reaction route and X-ray diffraction data revealed that the lattice parameters associated with orthorhombic cell (space group P21am) decrease with increase in La3+ content confirming the incorporation of La. In the frequency dependent dielectric measure…
The polar magnet CaBaCo$_{4}$O$_{7}$ is known to exhibit the largest magnetic-field-driven electric polarization change ($ΔP$) associated with an antiferromagnetic (AFM)-ferrimagnetic (FIM) transition in a narrow temperature range between 62 and 69 K. In this work, we investigate the effect of Ni doping on its multiferroic properties, by means of magnetization, electric polarization, dielectric constant, and magnetostriction measurements on single crystals of CaBaCo$_{3.9}$Ni$_{0.1}$O$_{7}$ up to 50 T. In the doped material, two kinds of AFM phases appear below 78 K, accompanying negative $ΔP$…
The giant magnetoelectric coupling is a very rare phenomenon which has gained a lot of attention for the past few decades because of fundamental interest as well as practical applications. Here, we have successfully achieved the giant magnetoelectric coupling in PbTi1-xVxO3 (x= 0-1) with the help of a series of generalized-gradient-corrected (GGA), GGA including on-site coulomb repulsion (U) corrected spin polarized calculations based on accurate density functional theory. Our total energy calculations show that PbTi1-xVxO3 stabilizes in C-type antiferromagnetic ground state for x>0.123. With …
The structural, dielectric, magnetic, and magnetoelectric (ME) properties of particulate composites containing lead-iron niobate and lead titanate piezoelectric 0.94[PbFe$_{0.5}$Nb$_{0.5}$O$_3$]-0.06[PbTi$_{0.5}$O$_3$] (PFN-PT) and Zn-substituted cobalt ferrite magnetostrictive CoFe$_{2-x}$Zn$_{x}$O$_4$ (CF$_{2-x}$Z$_{x}$O); 0.6(PFN-PT)/0.4(CF$_{2-x}$Z$_{x}$O), x=0, 0.025, 0.1, 0.2, 0.3 (with ratio of 60 Wt\% ferroelectric and 40 Wt\% ferrite); have been investigated. We investigated the ME voltage coefficient as a complex quantity for all composite samples using the dynamic piezomagnetic coef…
The present study reports on the structural and magnetic phase transitions in Pr-doped polycrystalline Tb0.6Pr0.4MnO3, using high-resolution neutron powder diffraction (NPD) collected at SINQ spallation source (PSI), to emphasize the suppression of the sinusoidal magnetic structure of pure TbMnO3 and the evolution to a collinear A-type antiferromagnetic ordering. The phase purity, Jahn-Teller distortion, and one-electron bandwidth for eg orbital of Mn3+ cation have been calculated for polycrystalline Tb0.6Pr0.4MnO3, in comparison to the parent materials TbMnO3 and PrMnO3, through the Rietveld …
Perovskite structure SrMnO$_3$ is a rare example of a multiferroic material where strain-tuning and/or cation substitution could lead to coinciding magnetic and ferroelectric ordering temperatures, which would then promise strong magnetoelectric coupling effects. Here, we establish the temperature and strain dependent ferroic phase diagram of SrMnO$_3$ using first-principles-based effective Hamiltonians. All parameters of these Hamiltonians are calculated using density functional theory, i.e., no fitting to experimental data is required. Temperature dependent properties are then obtained from …
The mutual control of the electric and magnetic properties of a multiferroic solid is of fundamental and great technological importance. We report here on the colossal magnetoelectric coupling effect of polycrystalline La0.2Pb0.7Fe12O19. A large classic ferroelectric hysteresis loop with full saturation and a strong magnetic hysteresis loop were observed simultaneously in polycrystalline La0.2Pb0.7Fe12O19 due to the coexistence of an off-centered FeO6 octahedron in its unit cell and electron spins in the partially filled 3d orbits of the Fe3+ ions. The coupling voltage and capacity demonstrate…
Multiferroics is a class of functional materials that simultaneously exhibit ferroelectricity and ferromagnetism in a single structure. We report here the integration of anti-ferroelectricity and ferromagnetism in a new M-type hexaferrite compound, in which 0.3 Sr ions was substituted by 0.2 La3+ ions in SrFe12O19 so as to keep the charge balance. This doped compound is expressed as a molecular formula of La0.2Sr0.7Fe12O19, which was confirmed by XRD to have the same structure as SrFe12O19 with a lattice contraction of 0.59%. Surprisingly, the doping effect turns La0.2Sr0.7Fe12O19 from ferroel…
