Dielectric response and magnetoelectric coupling in single crystal gallium ferrite

Abstract

Here we report the dielectric response and electric conduction behavior of magnetoelectric gallium ferrite single crystals studied using impedance analysis in time and temperature domain. The material exhibits two distinct relaxation processes: a high frequency bulk response and a low frequency interfacial boundary layer response. Calculated bulk capacitance as a function of temperature showed an anomaly at ferri- to paramagnetic transition temperature (∼ 300 K), suggestive of magneto-dielectric coupling in the material. Interestingly, we also witness an abrupt change in the activation energy at ∼ 220 K, in the vicinity of spin-glass transition temperature in GaFeO3

Temperature-dependent magnetic and electrical properties of Cr-doped AlFeO3 ceramics

“…Note, moreover, that the fitting Ea for the low-temperature range yields bulk activation energy of 0.11 to 0.04 eV. While observation of a bulk relaxation with such low activation energy is intriguing, similar observations are made in oxides such as single-crystal GaFeO 3 [44], oxygen deficient rutile TiO 2 [45], and Laand Gd-doped BaTiO 3 [46.]. Such dielectric relaxation is attributed to interplay between lattice and polaronic defects such as oxygen vacancies.…”

“…The presence of Cr 6+ ions has been reported in Gddoped LaCrO 3 orthochromite [44], however, where the values of Ea range from 0.21 eV to 0.39 eV with Gddoping content from 0 to 0.2, derived from the hopping of holes between Cr 3+ and Cr +6 . Accordingly, the similar activation energies from the electron and/or hole hopping of Fe or Cr ions with multi-valence states create a great challenge for distinguishing the different mechanisms.…”

Effect of annealing atmosphere on leakage and dielectric characteristics of multiferroic gallium ferrite

“…Among these, Mg‐doping of GaFeO 3 thin films has been shown to result in an improved leakage behavior, albeit no ferroelectric loops were reported . However, these studies do not offer much insights into defect chemistry of GFO except a few reports pointing toward the presence of oxygen vacancies . So, work is needed to understand the nature of defects giving rise to high conductivity in GFO, i.e., cations or anions vacancies or valence fluctuations of Fe ions.…”

Control of electrical leakage in magneto‐electric gallium ferrite via aliovalent substitution

“…Notwithstanding many useful characteristics of GFO, its utility in polycrystalline form is limited due to high electrical leakage, manifested in rounded and unsaturated ferroelectric loops, preventing possibility of its device applications . It has been proposed that the presence of Fe 2+ due to valence fluctuations of Fe ions and presence of oxygen vacancies could possibly be responsible for the high electrical leakage in GFO . Electrical leakage is a known problem in many dielectric, ferroelectric, or multiferroic oxides, attributed primarily to specific ionic or electronic defects or microstructural characteristics.…”

“…23,24 It has been proposed that the presence of Fe 2+ due to valence fluctuations of Fe ions and presence of oxygen vacancies could possibly be responsible for the high electrical leakage in GFO. [25][26][27] Electrical leakage is a known problem in many dielectric, ferroelectric, or multiferroic oxides, attributed primarily to specific ionic or electronic defects or microstructural characteristics. A very useful technique to control the electrical leakage and to improve ferroelectric properties of multiferroics (or ferroelectrics) is the atomic substitution by different ions, that is, doping or co-doping using iso-valent and aliovalent ions such as La, Nd, Ti, or Ni and various other ions.…”