5.             Conclusion
Single phase polycrystalline Bi0.85Sm0.1Ho0.05FeO3 is successfully prepared through solid state route and the variation of bond angle and bond length influencing the electrical and magnetic properties are investigated from Rietveld refinement analysis. The magnetization and ferroelectric polarization are found to be significantly improved in Bi0.85Sm0.1Ho0.05FeO3 than Bi0.9Sm0.1FeO3 and BiFeO3 ceramics. Temperature dependent dielectric constant shows an anomaly at 290° C nearer to TN, which is due to the intrinsic magnetoelectric coupling of Bi0.85Sm0.1Ho0.05FeO3 ceramic.  A clear change in area of P - E loop after magnetic pooling also conforms the signature of magnetoelectric coupling. Hence it is concluded that, Bi0.85Sm0.1Ho0.05FeO3 is one of the probable candidate in the family of BiFeO3 to enhance magnetoelectric effect at ambient temperature and helpful for device applications.
 
 
 
Acknowledgements
One of the author R. Rajesh would like to thank the following centres:
 SAIF, IIT Madras, Department of Nanoscience and Technology, Karunya University, Coimbatore,  Department of Physics,  Alagappa University , Karaikudi ,  ACIC, St. Joseph College, Trichy. The author KR acknowledges UGC for emeritus scheme.
 
 
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Figure Captions:
Fig 1(a) X- ray diffraction of BiFeO3, Bi0.9Sm0.1FeO3 and Bi0.85Sm0.1Ho0.05FeO3.                                                    (b) Predominant splitting of (104) and (110) planes of BiFeO3, Bi0.9Sm0.1FeO3 and Bi0.85Sm0.1Ho0.05FeO3.
Fig 2(a) and (b) Rietveld refinement of Bi0.9Sm0.1FeO3 and Bi0.85Sm0.1Ho0.05FeO3. The red plus symbols represent the observed data whereas calculated pattern is showed as solid green line. The difference pattern between the calculated and observed data is given as pink solid line. Brown vertical bars represent the allowed Bragg peak positions for their respective crystal structures while the red and green vertical bars indicates secondary phases of the corresponding crystal structure
 
 
Fig. 3(a) & (b) scanning electron micrograph of BiFeO3 and Bi0.85Sm0.1Ho0.05FeO3
Fig. 4(a) Magnetization as a function of applied field for BiFeO3, Bi0.9Sm0.1FeO3 and Bi0.85Sm0.1Ho0.05FeO3 at ambient temperature.
         (b) ABK plot of BiFeO3, Bi0.9Sm0.1FeO3 and Bi0.85Sm0.1Ho0.05FeO3 samples at ambient temperature
 
Fig. 5(a) Temperature dependent dielectric constant of Bi0.85Sm0.1Ho0.05FeO3 ceramic between the frequency ranges of 5 kHz to 5 MHz Dielectric anomaly observed at 290°C is indicated by an arrow mark.
            Inset of Fig. 5(a) Temperature dependent dielectric loss of Bi0.85Sm0.1Ho0.05FeO3 ceramic between the frequency ranges of 5 kHz to 5 MHz
Fig. 5(b) Temperature dependent resistivity of Bi0.85Sm0.1Ho0.05FeO3 ceramic between the frequency ranges of 1 kHz to 1 MHz
Fig. 5(c) Frequency dependent dielectric constant of BiFeO3, Bi0.9Sm0.1FeO3 and Bi0.85Sm0.1Ho0.05FeO3 at ambient temperature.
            Inset of Fig. 5(c) Frequency dependent dielectric loss of BiFeO3, Bi0.9Sm0.1FeO3 and Bi0.85Sm0.1Ho0.05FeO3 at ambient temperature.
 
Fig. 6(a) Ferroelectric hysteresis loop of BiFeO3, Bi0.9Sm0.1FeO3 and Bi0.85Sm0.1Ho0.05FeO3 at 100 Hz.
         (b) Leakage current density measurements as a function of applied electric field for BiFeO3, Bi0.9Sm0.1FeO3 and Bi0.85Sm0.1Ho0.05FeO3
 
Fig. 7(a) Ambient temperature magnetodielectric effect of Bi0.85Sm0.1Ho0.05FeO3 at 100 Hz.
 
Fig. 7(b) Ferroelectric hysteresis loops of Bi0.85Sm0.1Ho0.05FeO3 ceramic measured at a frequency of 100Hz before and after poling at a dc magnetic field of 9 kOe for 25 minutes
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
FIG. 1
 
 
 
 
FIG. 2
 
FIG. 3
 
 
 
                                   
 
 
FIG. 4
                                                       
 
 
FIG. 5
 
FIG. 6
 
 
 
 
FIG. 7
 
 
Sample
BiFeO3
Bi0.9Sm0.1FeO3               
Bi0.85Sm0.1Ho0.05FeO3    
Lattice Parameters
a = b = 5.5770Ȧ ; c = 13.862Ȧ
a = b = 5.5717Ȧ ; c = 13.835Ȧ
a = b = 5.5743Ȧ ;  c = 13.828Ȧ
Interfacial Angles
α = β = 90°  ; γ =120°
α = β = 90°  ; γ =120°
α = β = 90°  ; γ =120°
Atomic position
Bi  (0,  0,  0)            
Fe  (0,  0,  0.2208)
O   (0.44730,  0.0198,  0.9525)
Bi / Sm  (0,  0,  0)            
Fe  (0,  0,  0.2205)
O   (0.4458,  0.0186,  0.9516)
Bi/Sm/Ho  (0,  0,  0)       
Fe  (0,  0,  0.2205)
O   (0.4347,  0.00374,  0.9551)
Volume (Å3)
373.39
371.96
372.11
Bragg reflection ratio
 
 
 
BiFeO3  ( R3c)
84.8%
92%
100%
Bi2Fe4O9  (Pbam)
14 %
3.02%
 
 Bi25FeO40 (I23)
1.2%
4.98%
 
Density (gm / cm3)
8.348 
8.223
8.161
Bond angle (Fe1 - O - Fe2)
155.13°
155.128°
156.13
Bond length (Fe – O1)
1.9605 Ǻ
1.9604 Ǻ
1.9159 Ǻ
Bond length (Fe – O2)
2.0976 Ǻ
2.0971 Ǻ
2.1298 Ǻ
R - Factors              
 
wRp = 0.1742
RF2    = 0.2355
Rb       = 0.1373
 
wRp = 0.1292
RF2    = 0.5135
Rb       = 0.1664
 
wRp = 0.1277
RF2    = 0.1618
Rb      = 0.1423
 
Goodness of fit (GOF)
1.24
1.08
1.21
Table: I Rietveld refinement of BiFeO3, Bi0.9Sm0.1FeO3 and Bi0.85Sm0.1Ho0.05FeO3
 
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