Covalency driven modulation of paramagnetism and development of lone pair ferroelectricity in multiferroic Pb_3TeMn_3P_2O_{14}
Rafikul Ali Saha, Anita Halder, Tanusri Saha-Dasgupta, Desheng Fu, Mitsuru Itoh, Sugata Ray
aa r X i v : . [ c ond - m a t . m t r l - s c i ] F e b Covalency driven modulation of paramagnetism and developmentof lone pair ferroelectricity in multiferroic Pb TeMn P O Rafikul Ali Saha , Anita Halder , Tanusri Saha-Dasgupta ,Desheng Fu , Mitsuru Itoh , and Sugata Ray ∗ School of Materials Sciences, Indian Association for the Cultivation of Science,2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, India Department of Condensed Matter Physics and Material Sciences,S. N. Bose National Centre for Basic Sciences,Block JD, Sector 3, Saltlake, Kolkata -700106, India Department of Electronics and Materials Science,and Department of Optoelectronics and Nanostructure Science,Graduate School of Science and Technology, Shizuoka University,3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan and Materials and Structures Laboratory, Tokyo Institute of Technology,4259 Nagatsuta, Yokohama 226-8503, Japan
Abstract
We have investigated the structural, magnetic and dielectric properties of Pb-based langasitecompound Pb TeMn P O both experimentally and theoretically in the light of metal-oxygen co-valency, and the consequent generation of multiferroicity. It is known that large covalency betweenPb 6 p and O 2 p plays instrumental role behind stereochemical lone pair activity of Pb. The samehappens here but a subtle structural phase transition above room temperature changes the degreeof such lone pair activity and the system becomes ferroelectric below 310 K. Interestingly, this struc-tural change also modulates the charge densities on different constituent atoms and consequentlythe overall magnetic response of the system while maintaining global paramagnetism behavior ofthe compound intact. This single origin of modulation in polarity and paramagnetism inherentlyconnects both the functionalities and the system exhibits mutiferroicity at room temperature. ∗ [email protected] ntroduction . The story of stereochemically active cationic lone pairs, arising due to s - p mixing in metal assisted by covalency with the ligand p -orbitals and finally drivingferroelectricity within a polar unit cell, has always been an exciting point of discussion incondensed matter physics . There is a sizable number of systems where this mechanism plau-sibly works, such as, ferroelectric perovskites (PbTiO , BiMnO , BiFeO , SnTiO , CsPbF etc) , double perovskites (Pb ScTi . Te . O , Pb ScSc . Te . O , Pb MnWO ) , as wellas α -PbO , SnO, BiOF , Bi WO , BiMn O etc. Among these, systems which alsoaccommodate magnetic cations and consequent possibility of multiferroicity draws muchenhanced attention. The two most prominent examples of such multiferroics having signifi-cant roles of lone pair and covalency are BiFeO and BiMnO . Among these, BiFeO undergoes ferroelectric phase transition with T C = 1100 K and a G-type antiferromagnetictransition at a lower temperature (650 K), accompanied by an incommensurate spin cycloidstructure having a period of 620 ˚A . Due to this incommensurate spatially modulatedcycloid spin structure, linear ME effect is not observed in BiFeO , however, the polarizationbreaks the crystal symmetry and manifests itself in the appearance of an inhomogeneousME interaction (Lifshitz invariant), showing quadratic dependence of polarization on themagnetic field . On the other hand, BiMnO is one of the very few multiferroics that isferroelectric ( ∼
770 K) and ferromagnetic ( T C = 105 K) . In this case the ferroelectricityhas been explained by the presence of stereochemically active Bi s lone pair, developingfrom the mixing of the Bi 6 s and 6 p orbitals, activated by charge transfer from fully filledanionic orbital to the empty Bi 6 p orbital. As a result, the system becomes structurallynoncentrosymmetric below 770 K and a distinct magnetoelectric response of -0.6 % isobserved at the magnetic transition temperature .In this context we have explored rarely studied langasites ( A BC D O ), having lone pairbearing Pb ions and 3 d transition metal (TM) ions within TMO tetrahedral units. Tetra-hedral co-ordinations are traditionally more conducive for TM-O covalent interaction which plays a crucial role in deciding the degree of lone pair activity of Pb by manipulatingthe available electron density on the oxygen, sharing both TM and Pb connections. In thefamily of langasites, C and D site cations remain in tetrahedral coordination, while B and A sites form octahedral and decahedral network respectively . The network of A cationsforms topologically equivalent kagome lattice from well separated planes of corner sharingtriangles . Members of Langasite family are known to host multiferroism, non-linear opti-2al, pizoelectric, ferroelectric and dielectric properties , e.g., Fe based langasite compounds A B Fe D O ( A = Ba, Sr, Ca; B = Ta, Nb, Sb; D = Ge, Si) show frustration driven helicalmagnetic order, accompanied by a dielectric anomaly at the onset of magnetic transition .However, lone pair driven multiferroicity in langasites has not been explored till date.Pb TeMn P O can become important exactly in this context where changes in thedegree of stereochemical lone pair activity of Pb distorts the general non-polar structureinto a polar one, causing a shifting of magnetic Mn/P planes (M-P planes) towards theneighbouring Pb/Te containing planes (P-T plane) in the direction of positive c axis. Thisresults in formation of stripe-like distribution of pairwise closely placed M-P / P-T planeswithin the structure which in turn enhances the covalency as well as magnetic momentson otherwise nonmagnetic entities such as Pb , Te , P , and O − . This structuralchange brings forth spontaneous polarization in the system at around ∼
310 K, and thesynchronous redistribution of magnetic moments on the ions and shortened relative distancesamong them affect the overall paramagnetic state, which gets manifested in a clear signalof magnetoelectric coupling within the apparent paramagnetic phase, i.e. far above thelong range magnetic transition ( ∼ in spin-chain compounds and has been explained by the variations ofshort-range magnetic correlations within the paramagnetic phase.Overall, in this paper we present a new multiferroic with room temperature magneto-electric coupling arising from covalency affected stereochemical activity of lone pair andcoincident changes in local magnetic correlations.Experimental and theoretical details are elaborately presented in the Supplemental Ma-terial . Structure f rom x − ray dif f raction . The structural refinement of room temperature X-Ray diffraction (XRD) of PTMPO has been performed by considering noncentrosymmetricand polar trigonal space group ( P
3) (Lattice parameter and crystal structure are givenin Table S1 and S2 of the Supplemental Material ), consistent with previous literaturereports . Temperature dependent X-ray diffractions have been collected over a widetemperature range of 5-400 K. The Rietveld refinements of these collected XRD patternshave been carried out using the same trigonal space group P
3. Thermal variations of refinedlattice parameters, a , b , c and unit cell volume, are shown in Fig. 1 (a)-(c). Two anomaliesat ∼
310 K and ∼
120 K are observed in the temperature dependent lattice parameters as3ell as unit cell volume variations. We performed the 299 K XRD refinement using both P
321 and P respectrively. It is clearly evident from the fitting that the higher symmetry P
321 spacegroup could not capture the supper lattice peaks in the low temperature diffraction pattern(blue ellipse line in Fig. S1 (a) of Supplemental Material ). On the other hand, the superlattice peaks have been well reproduced while fitting using low symmetry P ). Most importantly, the roomtemperature synchrotron data also are very similar to our lab XRD results, as shown inFig. S1 (d), (e) and (f) of the Supplemental Material . This convincingly affirms theroom temperature ferroelectric phase ( P
3) for the studied sample. It is important to notethat the absence of superlatticepeaks in the 400 K XRD refinement (see Fig. S1 (c) of theSupplemental Material ) signifies the higher symmetric structure (space group: P P
321 structure (see Table S1 andS3 of the Supplemental Material ) but the symmetry gets lifted (polar P
3) with coolingand the polar structure only gets further distorted below 120 K.Due to this structural phase transition ( P
321 to P ). The lower symmetry P P C symmetry from P c axis (Fig. 2(a)-(b)). As a result,Mn-O bond lengths become shorter ensuring larger covalent interaction (see the Table I) andplausible enhancement of the stereochemical activity of the Pb lone pair. This shift alsoaffects the overall site symmetry as all the Pb and Mn triangles become scalene, as shown inFig. 2(c)-(d). This unit cell with lower symmetry becomes large, containing seven formulaunits per unit-cell. Interestingly, these scalene triangles of Pb, Mn, and Te are found to beconnected through a systematic 120 ◦ rotations (see Fig. S2 and Fig. S3 of the SupplementalMaterial ) and it may be anticipated that stereochemically active Pb (6 s ) lone pair isresponsible for such deformations of the structural motifs.However, it is primarily important to confirm the existence of stereochemically activePb lone pair at all temperatures, while the degree may change with structural transitions.If we divide the Pb-O polyhedron into two spheres (I and II), the difference between the4hortest Pb-O distances of the two spheres ( △ E ) provides a measure of the asymmetry,degree of delocalization and lone pair activity. The other notable parameter in this regardis △ E which is the difference between the shortest Pb-O distance in the polyhedron ofPTMPO and the known shortest Pb-O distance in compounds containing these elements.A large value of △ E and smaller value of △ E attribute higher stereochemical activity ofthe lone pair . Here, to estimate △ E , we considered the minimal distance d P b − O (2.40˚A) from Pb V O . Thus the values of △ E turn out to be 0.44 ˚A and 0.36 ˚A while △ E tobe -0.04 ˚A and 0.06 ˚A for P P
321 space groups respectively, indicating higher degreeof stereochemical activity of Pb lone pair in the P compounds . T heoretical calculations . We have carried out density functional theory (DFT) cal-culations in order to assess the covalency effect which is important for the stereochemicalactivity of the Pb lone pair. Since the goal of our first-principles calculation is to reveal thecovalency effect between different cations and oxygen and the effect of structural transitionon it, the analysis of electron structure was carried out on spin-polarized calculations. Theantiferromagnetic structure, which is the ground state magnetic structure is complex andleads to cancellation of covalency effect due to opposite alignment of spins, as ascertainedin vanishing moment of oxygen compared to its finite value in fully spin-polarized calcu-lation (see Table II). The calculations have been carried out both for the nonpolar (hightemperature P P
3) structures and the detailed density ofstates (DOS) are shown in Fig. 3(a) and (d), respectively. The stereochemical activity oflone pair active ions like Bi or Pb within oxide structures has been argued to originatefrom the hybridization between 6 s , 6 p orbitals at Bi/Pb site and 2 p orbitals at O site. Thedegree of stereochemical activity is thus crucially dependent on the energy level positions ofthese states, especially the position of 6 p . The 6 p -2 p hybridization turns out to be governingfactor in giving rise to directionality of the lone pair and driving the off-centric movement .Comparing between the projected DOS of PTMPO at high temperature non polar ( P P
3) phases we observe a marked change in the position of Pb6 p , it being closer to O 2 p by about 1.5 eV in the low temperature phase, compared to thatin the high temperature phase, suggestive of enhanced interaction between Pb 6 s - O 2 p antibonding orbitals with the empty Pb 6 p orbital . This has been quantitatively confirmedfrom our COHP (Crystal Orbital Hamilton Population) calculation where the integrated5OHP (ICOHP) values have been found to become double for the Pb-O connectivity whilegoing from P
321 to P ).Such an effect should obviously enhance the degree of Pb lone pair activity in the compoundat lower temperature. Interestingly, in the langasite structures, this also affects the energyposition of the orbitals and electron density on Te because Pb and Te share common oxygen.This effect is clearly reflected in projected DOS, which shows Te 5 p to be closer to oxygen2 p by 1 eV in the low temperature phase compared to that in high temperature phase. Asa result of this, there evolves an off-centric movement of otherwise nominally Te ion withtwo well defined coordination shells of neighboring oxygen atoms in the low temperaturephase (see Fig. 3. (f)), while at high temperature the off centric movement of Te vanisheswith only one coordination shell of neighboring oxygen atoms (see Fig. 3. (c)). Thus, clearlydipoles are created within the system.On top of it, the elemental magnetic moment possesses a noticeable change in the polarstructure relative to the high temperature nonpolar structure, in line with the strongercovalency effect of the polar structure (see table II). The charge density distribution in thetwo structures indicate that there could be one more dipole moment center that might becreated in the polar structure ( P
3) other than the polar geometry of TeO octahedra. Thestereochemically active lone pairs of Pb ( ns ) in Pb-Pb hexagon do not show any netpolarization due to the equal length of Pb-Pb distance in the P
321 phase, as shown in Fig.3. (c), while in the polar structure, Pb hexagon creates a net dipole moment along thenegative b direction with respect to the centre of mass, as shown in Fig. 3. (f). As Pb hexagon and TeO octahedra posses dipole moments along the negative b and negative c directions, respectively, a net dipole moment within a single Pb motif (where Te and Pbare present in the a-b plane) is generated along the b-c plane. Dielectric measurements . All the results shown above indicate towards realizing aferroelectric phase at room temperature in PTMPO which is next checked by dielectricmeasurements. The temperature dependence of the real part of the dielectric constant( ε ′ / ε ) and dielectric loss (tan δ ) at different frequencies (1 kHz to 1 MHz) in the temperaturerange of 5 to 400 K are shown in Fig. 4(a) and (b). A glass like phase transition (frequencydependent) near 120 K and another frequency independent anomaly near 315 K appears inthe data. Clearly, the anomaly near 315 K appears due to the structural phase transitionfrom high temperature nonpolar phase P
321 to low temperature polar phase P
3. Further6he polarization ( P ) with varying electric field ( E ) at room temperature (298 K) has beenmeasured, as indicated in Fig. 4(c), where clear P − E loop with saturation and remnantpolarization of 0.83 µ C/ cm and 0.3 µ C/ cm respectively, are observed at room temperature.Such a square loop along with sharp peaks in the switching current density ( J ) vs electricfield ( E ) curve at room temperature (Fig. 4(c)(sky shaded region)), clearly confirm existenceof ferroelectric ordering in the sample at room temperature. M agnetism, heat capacity and magnetodielectric . Next we focus on the magnetic prop-erties of the compound. Zero-field cooled (ZFC), field cooled cooling (FCC) and field coolheating (FCH) magnetization at 500 Oe, 5000 Oe and 10000 Oe were measured in thetemperature range of 2-400 K, as shown in Fig. 5(a). Clear antiferromagnetic transitionaround T N = 7 K is observed in all the ZFC, FCC and FCH curves, consistent with previousstudies .Interestingly, an unexpected effect is seen in the magnetic susceptibility at high temper-ature around the nonpolar to polar structural phase transition. A wide and thin hysteresisbetween the FCC and FCH data is observed around room temperature along with a distinctfeature in the FCH curve (Fig. 5(b)). Such a behavior is reminiscent of a first order phasetransition which is unusual for a purely paramagnetic state. In order to reconfirm, we haverepeatedly measured the M − T data of different batches of samples in different instrumentsand obtained the same result confirming the robustness of the observation. It has beendiscussed earlier that the shift of the M-P plane towards P-T plane at the phase transition,affects the local covalency, effective moments on all the atoms (see Table-I and II), and prob-ably the local magnetic correlations as well. It is likely that the local magnetic interactiongets affected quite substantially even though the system continues to remain a paramagnetglobally. We tend to express the two different paramagnetic phases as PM-II (polar phase)and PM-I (nonpolar phase) which must be differing at the local scale as indicated by thesusceptibility data. These features in magnetic susceptibility are further characterized bythe zero field heat capacity measurements ( C p versus T ). A sharp λ like anomaly, authen-tication mark of thermodynamic phase transition into a long range magnetic ordering hasbeen observed near 7 K in the C p versus T data (shown in the inset of Fig. 5 a)) which isin agreement with magnetic susceptibility data. Interestingly, we observe an anomaly justabove room temperature (see the inset of Fig. 5 b)), which maps the high temperaturemagnetic anomaly (bifurcation in FCC and FCH) and the structural phase transition.7urther we study the temperature dependent dielectric constant under 9 Tesla magneticfield, shown in Fig. 5(c) along with the zero field data. A significant change is observedbetween the with field ( H = 9T) and without field data near 270 K, as indicated in theinset to Fig. 5(c), signifying the presence of magnetoelectric coupling in the system. Thismagnetoelectric coupling is further established from the isothermal magnetoelectric data at270 K, as shown in Fig. 5(d). Further, there is no significant change in magnetocapacitancewith varying magnetic field at 315 K (see Fig. S5 of the Supplemental Material ) signifyingthe absence of magnetoelectric coupling above ferroelectric phase transition. It can be arguedthat the structural phase transition brings forth ferroelectricity in the system below 310 Kas a result of enhanced covalency and lone pair activity which at the same time affects themagnetism locally (introduction of the PM-II phase) and ensures a definite coupling betweenthe two as they originate from the same microscopic effect. Conclusion . We have reported the results of experimental and theoretical studies on Pbbased langasite compound PTMPO. A clear ferroelectric transition is developed near 310K. Stronger Mn-O covalent interactions helps to redistribute the charges among the othercation-oxygen bonds, which in turn induces crucial electronic changes and consequently, theindividual elemental magnetic moment gets changed in the system. The Mn-O covalencyeventually facilitates the lone pair activity within Pb, which further displaces the magneticMn motif in the system. As a result the system shows a first order structural phase transitionfrom P
321 to P Acknowledgment . RAS thanks CSIR, India for a fellowship. SR thanks TechnicalResearch Center of IACS. SR also thanks Department of Science and Technology (DST)[Project No. WTI/2K15/74], UGC-DAE Consortium for Research, Mumbai, India [ProjectNo. CRS-M-286] for support. AH and TSD acknowledge the computational support ofThematic Unit of Excellence on Computational Materials Science, funded by Nano-mission8f Department of Science. A. Walsh, D. J. Payne, R. G. Egdell and G. W. Watson, Chem. Soc. Rev. , 4455 − X. He and K. Jin, Phys. Rev. B , 224107 (2016). N. A. Hill and K. M. Rabe, Phys. Rev. B , 8759 (1999). R. Seshadri and N. A. Hill, Chem. Mater , 2892-2899 (2001). L. M. Volkova and D. V. Marinin, J Supercond. Nov. Magn. , 2161-2177 (2011). K. C. Pitike, W. D. Parker, L. Louis and S. M. Nakhmanson, Phys. Rev. B , 035112 (2015). E. H. Smith, N. A. Benedek, and C. J. Fennie, Inorg. Chem. , 8536 − S. A. Larregola, J.A. Alonso, M. Alguero, R. Jimenez, E. Suard, F. Porcher and J.C. Pedregosa,Dalton Trans., S. A. Ivanov, A. A. Bush, A. I. Stash, K. E. Kamentsev, V. Ya. Shkuratov, Y. O. Kvashnin, C.Autieri, I. D. Marco, B. Sanyal, O. Eriksson, P. Nordblad, and R. Mathieu, Inorg. Chem. ,2791 − G. W. Watson and S. C. Parker, Phys. Rev. B , 8481 (1999). R. Seshadri, Proc. Indian Acad. Sci. (Chem. Sci.) , 487-496 (2001). C. E. Mohn, and S. Stølen, Phys. Rev. B , 014103 (2011). D. K. Shukla, S. Mollah, Ravi Kumar, P. Thakur, K. H. Chae, W. K. Choi, and A. Banerjee,J. Appl. Phys. , 033707 (2008). S. Lee, M. T. Fernandez-Diaz, H. Kimura, Y. Noda, D. T. Adroja, S. Lee, J. Park,V. Kiryukhin,S.-W. Cheong, M. Mostovoy, and Je-Geun Park, Phys. Rev. B , 060103(R) (2013). P. Baetting, R. Seshadri, and N. A. Spaldin J. Am. Chem. Soc. , 9854 − R. T. smith, G. D. Achenbach, R. gerson, and W. J. James, J. Appl. Phys. , 70 (1968). I. Sosnowska, T. Peterlin-Neumaier and E.J. Steichele, J. Phys. C: Solid State Phys. , 4835 − R. Przenioslo, M. Regulski, and I. Sosnowska, J. Phys. Soc. Jpn. , 084718 (2006). A. M. Kadomtseva, A. K. Zvezdin, Yu. F. Popov, A. P. Pyatakov, and G. P. Vorob’ev, JETPLetters, , 571 −
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321 and P Bond length (˚A) Bond length of Longer site (˚A) Bond length of Shorter site (˚A)( P
321 Space group) ( P TABLE II. Magnetic moment of PTMPO compounds in µ B . Space group Mn Pb Te P O P
321 4.632 0.008 0.034 0.009 0.021 P c () V () T (K) Volume of unit celllatice parameter c a () latice parameter a
20 40 60 80 I n t e n s i t y ( a . u . ) XRD at 400 K
Space Group: P R exp = 12.01, = 6.01 I n t e n s i t y ( a . u . ) Space Group: P XRD at 299 K R exp = 11.69, = 5.68 (in degree) I n t e n s i t y ( a . u . ) R exp = 12.1, = 6.08Space Group: P XRD at 5 K a) c) b) d) e) f)
FIG. 1. a), b) and c) Thermal variation of lattice parameters and volume of unit cell of PTMPO. d),e) and f) are the refined XRD pattern of 400 K, 299 k and 5 K data respectively. Open black circlesrepresent the experimental data and continuous red line represents the calculated pattern. Theblue line represents the difference between the observed and calculated pattern. Green scatteredline are Bragg peak. a) b) c) d) IJ= 3.672 , JK= 3.675 , KI=3.532 A BCI JK
AB= 5.787 , BC= 6.018 , CA=6.017
Equilateral triangle
M NO P QR MN= 3.704 , NO= 3.721 , OM=3.805 PQ= 5.917 , QR= 5.885 , RP=5.947
AB=BC=CA= 5.91 IJ=JK=KI= 3.68
BJAKC I
400 K ( P P O P Mn Te Pb
FIG. 2. a) and b) are the a − c plane of P
321 and P a − b planeof P
321 and P a) P b) Te and O centres coincide atAll Pb-Pb distances in hexogon are equal c) d) P Pb lone pair Te e) Te and O centres coincide at (0, 0, 1) All Pb-Pb distances in hexogon are unequal p Pb p f) Te (0.57, 0.72, 1) O (0.57, 0.72, 1.03) p Te FIG. 3. a), b) and c) Partial DOS, Electron localization function within a unit cell(The isosurfacesare vizualized for a value of 0.3) and Pb hexagon and TeO octahedra of P
321 structure ofPTMPO respectively. d), e) and f) Partial DOS, Electron localization function within a unit cell(The isosurfaces are vizualized for a value of 0.3) and Pb hexagon and TeO octahedra of P ' - T c
310 K T (K) t a n -100 -50 0 50 100-1.2-0.60.00.61.2 -100-50050100 E (kv cm -1 ) T =298 K P ( C c m - ) J ( A c m - ) c) a) b) FIG. 4. a) and b) Temperature dependence of real part of dielectric constant ε ′ / ε and tan δ lossdata of PTMPO at different frequencies. c) Electric field dependent polarization (pink line) andswitching current behaviour (green line)of PTMPO at room temperature. a) b) c) d) -20000 -10000 0 10000 200000.000.020.040.06
500 kHz H (Oe) ( C p ( H ) - C ( )) * * C ( ) -
270 K
280 320135140145
210 280 3500.040.050.06 C p ( J m o l - K - M n - ) T (K) FCC
FCH ( e m u m o l - O e - ) T (K) H = 1 Tesla ' - with applied field 9 T zero field ' - T (K)
270 28831.231.8 T (K) ( e m u m o l - O e - ) T (K) C p ( J m o l - K - M n - ) T (K) FIG. 5. a) M − T at 500 Oe, 5000 Oe and 10000 Oe of PTMPO. Open red, solid red triangleand solid red circle represent the ZFC, FCC and FCH of 500 Oe data. Open green, solid greentriangle and solid green circle represent the ZFC, FCC and FCH of 5000 Oe data. Open blue, solidblue triangle and solid bule circle represent the ZFC, FCC and FCH of 10000 Oe data. Inset ofa) shows Heat capacity data at low temperature. b) Red curve and blue curve are the FCC andFCH at 10000 Oe data. Inset of b) shows Heat capacity data at high temperature. c) Temperaturedependent dielectric constant with 0 field and 9 Tesla field and inset indicates the gap betweenthem. d) Magnetodielectric data at 270 K.at 500 Oe, 5000 Oe and 10000 Oe of PTMPO. Open red, solid red triangleand solid red circle represent the ZFC, FCC and FCH of 500 Oe data. Open green, solid greentriangle and solid green circle represent the ZFC, FCC and FCH of 5000 Oe data. Open blue, solidblue triangle and solid bule circle represent the ZFC, FCC and FCH of 10000 Oe data. Inset ofa) shows Heat capacity data at low temperature. b) Red curve and blue curve are the FCC andFCH at 10000 Oe data. Inset of b) shows Heat capacity data at high temperature. c) Temperaturedependent dielectric constant with 0 field and 9 Tesla field and inset indicates the gap betweenthem. d) Magnetodielectric data at 270 K.