Effect of magnetic spins flipping process on the dielectric properties of α-Fe1.6Ga0.4O3 system

Abstract

The α-Fe1.6Ga0.4O3 (Ga doped α-Fe2O3) sample has been stabilized in rhombohedral structure. The sample is a canted ferromagnet at 300 K and above. The spins structure starts flipping from in-plane direction to out of plane direction of the rhombohedral structure to exhibit an antiferromagnetic order below a typical temperature ∼ 215 K, known as Morin transition. The magnetic and dielectric properties of α-Fe1.6Ga0.4O3 system have been discussed in the temperature range 123 K to 350 K to examine the effect of magnetic spins flipping process on dielectric properties. The dielectric constant has shown an anomalous peak at ∼ 310 K, followed by a rapidly decrease of dielectric constant with temperature and becomes weakly temperature dependent below Morin transition. The temperature dependent dielectric constant is accompanied with the changes in electrical conductivity, dielectric loss and phase shift of the current with respect to applied ac voltage across the material. The magnetization and dielectric constant showed a linear relation over a wide range of temperature across the Morin transition. The dielectric constant at room temperature decreases under magnetic field, which indicates magneto-dielectric effect in the system. The signature of magneto-dielectric effect reveals a coupling between spins degrees of freedom (magnetic order) and charge degrees of freedom (electric polarization) in corundum structured non-traditional ferroelectric systems.

Magnetic field cycling effect on the non-linear current-voltage characteristics and magnetic field induced negative differential resistance in α-Fe1.64Ga0.36O3 oxide

“…C. Papaioannoua et al 10 suggested a possible charge-spin coupling in hematite. Our recent work 11 has highlighted the effect of magnetic spins flipping on magneto-electric coupling in α-Fe 1.6 Ga 0.4 O 3 system. The ferromagnetic semiconductor properties of Ga doped α-Fe 2 O 3 system are not like conventional III-V ions based diluted ferromagnetic semiconductor.…”

Electric field controlled magnetic exchange bias and magnetic state switching at room temperature in Ga-doped α-Fe2O3 oxide

“…The enhancement of spin-lattice coupling and small atomic displacement within rhombohedral structure of Ga doped hematite are indicated from Micro-Raman spectra. The dielectric peak in the temperature regime (290 K-310 K), where Fe 3+ spins started flipping from in-plane direction (canted FM state) to out of plane direction [32,42], indicated (canted) spin order induced magneto-electric coupling in Ga doped hematite system. We restrict our discussion for the origin of electric polarization in Ga doped hematite system based on the models of spin induced ferroelectricity [5,24].…”

“…At the same time, magnetic coercivity decreased with the increase of Ga content in hematite structure. These features indicated a modified magnetic structure in Ga doped hematite system [29,[31][32].…”

“…The band at around 1320 cm -1 (magnon-phonon mode) in Micro-Raman spectra confirmed a strong spinlattice coupling in rhombohedral structure of Ga doped hematite system. The structural and magnetic properties for some of the Ga doped hematite samples in rhombohedral phase have been discussed in earlier works [29,[31][32]. On the other hand, mechanical alloying and subsequent vacuum annealing were not enough to produce single phased rhombohedral structure for the composition α-FeGaO3.…”

“…In an attempt of searching new magnetoelectrics, we have taken an extensive research program to develop materials with room temperature ferromagnetism and electric field controlled magnetic state based on rhombohedral phase of metal doped hematite system. We developed Ga doped hematite system in rhombohedral structure (α-Fe2-xGaxO3) with canted ferromagnetic state at room temperature and good signature of ferroelectric polarization [29][30][31], although electric field dependence polarization curves are not completely free from leakage due to relatively high conductivity of the samples [32][33]. In this work, we establish Ga doped α-Fe2O3 system as a new magnetoelectric material, where magnetic state at room temperature is controlled by external electric field and switching of magnetic state is sensitive to ON and OFF modes, as well as to the change of polarity of applied electric field.…”