Anomalous coercivity enhancement with temperature and tunable exchange bias in Gd and Ti co-doped BiFeO₃multiferroics

Abstract

We have investigated the effect of temperature on magnetic properties of Bi0.9Gd0.1Fe1−xTixO3 (x = 0.00-0.20) multiferroic system. Unexpectedly, the coercive fields (Hc) of this multiferroic system increased with increasing temperature. The coercive fields and remanent magnetization were higher over a wide range of temperatures in sample x = 0.10 i.e. in sample having composition Bi0.9Gd0.1Fe0.9Ti0.1O3 than those of x = 0.00 and 0.20 compositions. Therefore, we have carried out temperature dependent magnetization experiments extensively for sample x = 0.10. The magnetic hysteresis loops at different temperatures exhibit an asymmetric shift towards the magnetic field axes which indicate the presence of exchange bias effect in this material system. The hysteresis loops were also carried out at temperatures 150 K and 250 K by cooling down the sample from 300 K in various cooling magnetic fields (H cool ). The exchange bias field (HEB) values increased with H cool and decreased with temperature. The HEB values were tunable by field cooling at temperatures up to 250 K.

Predicting High Magneto‐Electric Coupling in Gd Substituted BiFeO3

“…The large change in H c could be due to large change in indicating the presence of high magnetoelectric coupling in BGFO10 compound compared to other investigated compounds. The decrease in H c at low temperature and magneto‐electric properties have also been reported in Gd substituted BFO …”

“…The decrease in H c at low temperature and magneto-electric properties have also been reported in Gd substituted BFO. [31,32] The ZFC and FC magnetization measurements are carried out under a magnetic field of 1 kOe between the temperatures 5 and 300 K for BFO and BRFO10 compounds as shown in Figure 8. The decrease in magnetization from 300 to 100 K indicates the antiferromagnetic (AFM) nature of the compounds.…”

The exchange bias behavior of BiFeO3 nanoparticles with natural core-shell structure

“…While with the decrease of particle size, surface effect usually leads to a breaking of the sublattice pairing in antiferromagnet and results in a net surface magnetic moment. Therefore, BFO nanoparticles can be modeled by a superposition of an antiferromagnetic (AFM) core and a ferromagnetic (FM) surface 8,10–12 . The exchange coupling at the AFM/FM interface of a core-shell structure often leads to a phenomenon called “exchange bias”, which draws significant interests in recent years due to its important potential technological applications in various magnetic devices 13–18 .…”

“…The exchange coupling at the AFM/FM interface of a core-shell structure often leads to a phenomenon called “exchange bias”, which draws significant interests in recent years due to its important potential technological applications in various magnetic devices 13–18 . Recently, exchange bias effect was observed in BFO and its doped particles, and the results obtained by different research groups reveal that both the magnitude of the exchange bias field ( H E ) and its temperature-dependent behavior show obvious sample dependence 12,19–22 . While the origin of such complex sample-dependent behavior is still unclear and needs further investigation.…”

The 10% Gd and Ti co-doped BiFeO3: A promising multiferroic material

“…6 (b) shows an enlarged view of the M-H hysteresis loop carried out at 20 K. A tiny loop at the center of the hysteresis with a coercivity of 1979 Oe and remanent magnetization of 0.247 emu/g was observed at 20 K. The coercivity was reduced anomalously at 20 K compared to that at 300 K due to a competition between the magnetic anisotropy and the magnetoelectric coupling of this material as explained in details in Ref. [20].…”