Multiferroic composites are promising candidates for magnetic field sensors, next-generation low power memory and spintronic devices, as they exhibit much higher magnetoelectric (ME) coupling and ...coupled ordering parameters compared to the single-phase multiferroics. Hence, the 3-0 type particulate multiferroic composites having general formula (1 - Φ)PbFe
Nb
O
-ΦCo
Zn
Fe
Mn
O
(Φ = 0.0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, (1 - Φ) PFN-ΦCZFMO) were prepared using a hybrid synthesis technique. Preliminary structural and microstructural analysis were carried out using XRD and FESEM techniques, which suggest the formation of 3-0 type particulate composite without the presence of any impurity phases. The multiferroic behaviour of the composites is studied with polarization versus electric field (P-E) and magnetization versus magnetic field (M-H) characteristics at room temperature. The nature of ME coupling was investigated elaborately by employing the Landau free energy equation along with the magneto-capacitance measurement. This investigation suggests the existence of biquadratic nature of ME coupling (P
M
). The magneto-electric coupling measurement also suggests that strain mediated domain coupling between the ferroelectric and magnetic ordering is responsible for the magneto-electric behaviour. The obtained value of direct ME coefficient 26.78 mV/cm-Oe for Φ = 0.3, found to be higher than the well-known single-phase materials and polycrystalline composites.
Bismuth ferrite is doped with a dilute concentration of cobalt, BiFe1−XCoXO3; X=0, 0.01, 0.02 is prepared by sol-gel auto combustion technique. X-ray diffraction data refined via Reitveld method ...shows single phase and shrinkage in cell volume for Co doped BiFeO3. Various magnetic ground states viz. superparamagnetic, glassy antiferromagnetic and glassy ferrimagnetic behavior is observed for X=0, 0.01, 0.02, respectively. A first-order magnetic transition is observed in the Arrott plot data of cobalt doped BiFeO3. Possibility of thermally induced magnetic transition is also seen in the magnetization data of cobalt doped BiFeO3. A model based on the existing spinoidal cyclic arrangement of spins is proposed to explain the observed data. Finally, a very dilute concentration of Co+3 in BiFeO3 is found sufficient to tailor the magnetic properties.
► A dilute concentration of Co-doped BiFeO3 is prepared by sol-gel method which is found to be impurity free confirmed by Reitveld Method. ► A first order magnetic transition is observed in the doped samples. ► A cycloid spin model is proposed which strengthen the observed transition.
•CoFe2O4/Cr2O3 nanocomposite is studied for the possession of magnetoelectricity.•Magnetoelectricity is observed up to 340 K i.e., above TN of Cr2O3.•Weak room temperature ferromagnetism is observed ...for the nanocomposite.•Impedance and modulus analysis of the nanocomposite reveal single relaxation mechanism.
Cobalt ferrite CoFe2O4 (CFO)/chromium oxide Cr2O3 (CR) nanocomposite is prepared by following the sol-gel autocombustion method in order to study its magnetoelectric (ME) properties. The presence of both the CFO (cubic) and CR (rhombohedral) phases is confirmed from the Rietveld refinement results of X-ray diffraction (XRD) patterns. Field emission scanning electron micrograph (FESEM) display the homogeneous distribution of particles with the average particle sizes of ~50–300 nm. A small opening of hysteresis in the magnetization (M)-magnetic field (H) plot signifies the existence of weak ferromagnetism in the sample. The frequency dependence of impedance responses subjected to applied magnetic fields are well described by impedance based Havriliak-Negami expression and revealed the presence of single relaxation which is attributed to the grains response. The involvement of p-type polaronic relaxation is confirmed from the obtained value of activation energy ≈0.39 eV. More interestingly, the direct magnetoelectric measurement shows the existence of linear magnetoelectricity up to 340 K and therefore provide applications in various ME-based devices.
•Demonstration of spin-phonon coupling in trirutile magnetoelectric Fe2TeO6.•Dimeric (d(5/2)-d(5/2)) interaction induced short-range magnetic correlation.•Exploration of unknown magnetic anomaly at ...150 K below the familiar sharp transition (TN ∼ 210 K) corresponding to long-range order.•µSR study reveals of three dynamically distinguishable temperature regime as (I) T > TN, (II) TN > T > 150 K, and (III) T < 150 K.
Spin-phonon coupling originated from spin-lattice correlation depends upon different exchange interactions in transition metal oxides containing 3d magnetic ions. Spin-lattice coupling can influence the coupling mechanism in magnetoelectric material. To understand the spin–lattice correlation in inverse trirutile Fe2TeO6 (FTO), magnetic properties and phonon spectra are studied. Signature of short-range magnetic correlation induced by 5/2–5/2 dimeric interaction and magnetic anomaly at 150 K is observed apart from the familiar sharp transition (TN ∼ 210 K) corresponding to long-range order by magnetization and heat capacity measurements. The magnetic transitions and the spin dynamics are further locally probed by muon spin resonance (μSR) measurement in both zero fields (ZF) and longitudinal field (LF) mode. Three dynamically distinct temperature regimes; (i) T > TN, (ii) TN > T > 150 K, and (iii) T < 150 K, are observed. A change in the spin dynamics is realized at 150 K by μSR, though previous studies suggest long-range antiferromagnetic order. The renormalization of phonon frequencies observed in Raman spectra below 210 K suggests the existence of spin-phonon coupling in the material. The coupling strength is quantified as in the range 0.1–1.2 cm−1 following the mean-field and two-spin cluster approximations. We propose that the spin-phonon coupling mediated by the Fe-O2-Fe interbilayer exchange play a significant role in magnetoelectric ME coupling observed in the material.
•Room temperature weak ferromagnetism in polycrystalline Bi0.85Gd0.05La0.1FeO3.•Plausible multiferroic properties at room temperature in polycrystalline Bi0.85Gd0.05La0.1FeO3.•Magneto-electric ...coupling in polycrystalline Bi0.85Gd0.05La0.1FeO3.
The structural, magnetic and magneto-electric (ME) properties of polycrystalline BiFeO3 and Bi0.9–xGdxLa0.1FeO3 (x = 0.00 and 0.05) samples have been investigated. X-ray diffraction patterns confirm the formation of single phases in all the samples with ‘R3c’ space group. Magnetic anisotropy and ferroelectric hysteresis behaviour are observed in Bi0.85Gd0.05La0.1FeO3 through magnetization and polarization measurements respectively. In addition, the same compound shows weak ferromagnetism at room temperature with a significantly enhanced remnant magnetization of ~ 23.6emu.mol−1, concomitant with an exchange bias. ME measurements on the compound show a non-linear dependence of magnetic and electric vectors.
•Acrylamide polymer gel template method has been used to prepare single phase DyMnO3.•Heat capacity measurement shows three transitions due to TN(Dy), Tlock and TN(Mn).•Magnetic field strongly affect ...TN(Dy) and Tlock as observed in heat capacity data.•The magnetic study reveals the presence of two transitions due to TN(Dy) and Tlock.•Increase in weak ferromagnetic behaviour with decrease in temperature.
Single phase polycrystalline DyMnO3 (DMO) was synthesized using acrylamide polymer gel template method. We report the structural, magnetic, specific heat and dielectric properties of DMO over wide experimental conditions. Room temperature XRD pattern shows the formation of singe phase material without any impurity. The magnetic properties such as magnetization versus temperature (M vs. T) and magnetization versus magnetic field (M vs. H) were studied around the transition temperatures region. The temperature dependent magnetization data suggest two phase transitions corresponding to the lock-in temperature below which ferroelectric ordering exist (around 19 K; Tlock) and antiferromagnetic (AFM) ordering of Dy spin (around 8 K; TN (Dy)). The magnetic hysteresis obtained were fitted to extract weak ferromagnetic (FM) and antiferromagnetic/paramagnetic (AFM/PM) contribution to the magnetic data. The order of magnetic transitions were analyzed from Arrott plot. The temperature dependent specific heat measurement shows all three phase transitions corresponding to (i) AFM ordering of Mn spin (around 38 K; TN(Mn)), (ii) Tlock transition and (iii) TN(Dy) transition. The effect of magnetic field to the transitions were studied using specific heat capacity measurement. The peak intensity of TN(Dy) decreases on the application of magnetic field whereas peak intensity of Tlock increases with increase in magnetic field in specific heat measurement. Further the third anomaly, TN (Mn) remains more or less unaffected by the application of magnetic field. The intrinsic dielectric behaviour of the material was observed up to 160 K, above this temperature there is large increase in dielectric value due to the contribution from Maxwell- Wagner polarization.
In this study, manganese substituted strontium hexaferrite (SrFe12−xMnxO19; x = 0, 3, 5, and 7) prepared by the sol–gel auto-combustion method are studied. We observed that the substituted Mn ...preferentially goes to the 2a and 12k sites of Fe. Raman modes related to the 12k site suggest the stiffening of the lattice. The transformation of the grain's shape from hexagonal (x = 0 and 3) to rhombohedral (x = 7) was observed, as shown in the micrographs obtained from FESEM. The thermomagnetic curves show the shift of TC to lower temperatures with the increase in the Mn content. From x = 5 onwards, the growth of another magnetic phase (FiM2) of lower coercivity apart from the parent phase (FiM1) of higher coercivity is seen. The FiM2 phase was found to increase with the Mn content in the sample (16.4(3)% for x = 5 but 66.2(5)% for x = 7). Although the magnetization for both FiM1 and FiM2 decreases with the increase in temperature, both magnetic phases behave in contrast to each other for x = 5 and x = 7. The study suggests a transformation of the compound from high magnetic anisotropy (x = 0) to low magnetic anisotropy (x = 7). The x = 5 composition sample displays the highest value of the first-order ME coefficient (0.83(2) mV × cm−1 × Oe−1). The observed value for x = 5 composition is ∼2.5 times higher than that of the parent x = 0 composition sample (0.33(2) mV × cm−1 × Oe−1). The studies thus suggest that the x = 5 composition is one of the viable candidates for magnetoelectric applications.
A very handy setup is developed for the measurement of magnetoelectric (ME) voltage as a function of magnetic field and temperature. Using this setup, first and second order ME coupling coefficients ...of parent and cobalt substituted BiFeO3 are obtained. Study of these ME coefficients suggests involvement of magnetic disorder can enhance the ME couplings by many folds. In the intrinsic region a nearly same value of the first order coefficient for all the three samples are found. The behavior of higher order coefficient shows that parent BiFeO3 is of mono-glassy character whereas indications of multiglass nature is seen in the cobalt substituted BiFeO3. This study suggests that, a very light substitution of Cobalt at the Fe site may leave the first order coefficients unperturbed but may initiate multiglassiness in the sample, which is highly desirable for enhancing the magnetoelectricity.
•Magnetoelectric (ME) measurement setup is made that can operate within 125 K–400 K.•Magnetic field dependent ME voltage is measured for BiFe(1−x)CoxO3 (x = 0,0.01,0.02).•Temperature dependent 1st and 2nd order ME coefficient is measured for all samples.•Involvement of magnetic disorder in temperature dependent ME coefficient is found.
In this study, manganese substituted strontium hexaferrite (SrFe
Mn
O
;
= 0, 3, 5, and 7) prepared by the sol-gel auto-combustion method are studied. We observed that the substituted Mn ...preferentially goes to the 2a and 12k sites of Fe. Raman modes related to the 12k site suggest the stiffening of the lattice. The transformation of the grain's shape from hexagonal (
= 0 and 3) to rhombohedral (
= 7) was observed, as shown in the micrographs obtained from FESEM. The thermomagnetic curves show the shift of
to lower temperatures with the increase in the Mn content. From
= 5 onwards, the growth of another magnetic phase (FiM2) of lower coercivity apart from the parent phase (FiM1) of higher coercivity is seen. The FiM2 phase was found to increase with the Mn content in the sample (16.4(3)% for
= 5 but 66.2(5)% for
= 7). Although the magnetization for both FiM1 and FiM2 decreases with the increase in temperature, both magnetic phases behave in contrast to each other for
= 5 and
= 7. The study suggests a transformation of the compound from high magnetic anisotropy (
= 0) to low magnetic anisotropy (
= 7). The
= 5 composition sample displays the highest value of the first-order ME coefficient (0.83(2) mV × cm
× Oe
). The observed value for
= 5 composition is ∼2.5 times higher than that of the parent
= 0 composition sample (0.33(2) mV × cm
× Oe
). The studies thus suggest that the
= 5 composition is one of the viable candidates for magnetoelectric applications.
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