Magnetodielectric Effect and Tunable Dielectric Properties of LaMn_1−xFe_xO₃

Abstract

The dielectric properties of LaMn1−xFexO3 (LMFO, 0.1≤x≤0.5) under magnetic fields and electrical biases have been studied. A considerable low‐field magnetodielectric (MD) effect is observed for x≤0.2, but it is suppressed by further Fe substitution. Besides the giant MD effect, the dielectric constants can also be tuned by dc electrical bias, and a reduction of more than 70% for x≤0.2 under a low bias of 40 V/cm is achieved. These results together with the impedance characteristics can be explained by the contributions of barrier layers at interfacial and grain boundaries as well as the magnetoelectric coupling. The giant dielectric response and tunability under both low magnetic and electric fields in the nonferroelectrics may be advantageous for applications.

Lattice Defects Induce Multiferroic Responses in Ce, La‐Substituted BaFe0.01Ti0.99O3 Nanostructures

“…A negative MR dominated by the grains of the bulk samples, the positive MC effect produce, but the MC shown in Fig. is negative . The MR related to spin‐polarized tunneling across grain boundaries or interfaces may induce a negative MC, the dielectric loss should increase with increasing magnetic fields .…”

“…The concept of MD/MC was first observed on DyMnO 3 , for which the electric polarization is induced by a cycloidal spiral ordering . This effect is achieved through a combination of magnetoresistance (MR) and the Maxwell–Wagner effect.…”

“…The MR related to spin‐polarized tunneling across grain boundaries or interfaces may induce a negative MC, the dielectric loss should increase with increasing magnetic fields . The MD/MC is the change in dielectric constant (ε), [ε(H)−ε(0)]/ε(0), where ε( H ) and ε(0) denotes the dielectric constants at applied dc bias magnetic field H and zero field . Figure shows the change in the real part of the relative dielectric permittivity and tanδ (inset) of Ce, La‐doped BFTO nanoaggregation at frequencies 1 kHz, 10 kHz, and 1 MHz, as a function of magnetic field H dc and measured at room temperature.…”

“…The magnetism due to partially filled d orbitals (ordering of spins of electrons in incomplete ionic shells) and ferroelectricity by off‐centered displacement, d 0 (relative shifts of negative and positive ions that induce surface charges) are essential for multiferroicity in single‐phase multiferroic systems . The multiferroic materials have also magnetodielectric/capacitance (MD/MC) effect that mutually coupled magnetic and dielectric properties for those applications where the dielectric constant may control by the magnetic field …”

Room temperature multiferroicity in Bi4.2K0.8Fe2O9+δ

“…Although the resistance of the nanobelts decreases slightly in the temperature range from 280 K to 330 K under a field of 50 kOe, the MD effect in the nanobelts cannot be originated by a well-known Maxwell–Wagner capacitor configuration with considering the magnetoresistance (MR) effect2829. Firstly, for a negative MR dominated by the grains of the bulk samples in such a scenario, it will generally cause a positive MD effect30, but the MD coefficient shown in Fig. 6d is always negative in our case.…”