Magnetocapacitance

About: Magnetocapacitance is a research topic. Over the lifetime, 497 publications have been published within this topic receiving 23846 citations.

Magnetocapacitance and dissipation factor of epitaxial graphene-based quantum Hall effect devices

Abstract: We investigate the properties of the magnetocapacitance and dissipation factor of epitaxial graphene Hall bars with different electrode configurations to gain insight into the underlying physical mechanisms. The dependence of magnetocapacitance and dissipation factor on the magnetic field shows how the screening ability of the two-dimensional electron gas (2DEG) changes at the transition from the nonquantized to the quantized state. Both magnetocapacitance and dissipation factor exhibit a characteristic and correlated voltage dependence, which is attributed to the alternating contraction and expansion of the nonscreening 2DEG regions due to the alternating local electric field. Two regimes with seemingly different voltage dependencies are explained as the limiting cases of weak and strong electric fields of the same general voltage dependence. Electric fields in the plane of the 2DEG are found to cause about three orders of magnitude more ac dissipation than perpendicular electric fields. This strong directionality is attributed to the fact that the electrons are mobile in the plane of the 2DEG but are confined in the third dimension. In the quantized state, not only the screening edge of the 2DEG but also compressible puddles embedded in the bulk cause ac dissipation, as follows from the measured frequency dependence. Finally, characteristic parameters like the width of the screening edge, the threshold voltage, and the charging time of the compressible puddles are determined.

Opening an energy gap in an electron double layer system at the integer filling factor in a tilted magnetic field

Abstract: We employ magnetocapacitance measurements to study the spectrum of a double layer system with gate-voltage-tuned electron density distributions in tilted magnetic fields. For the dissipative state in normal magnetic fields at filling factor v=3 and 4, a parallel magnetic field component is found to give rise to the opening of a gap at the Fermi level. We account for the effect in terms of parallel-field-caused orthogonality breaking of the Landau wave functions with different quantum numbers for two subbands.

Magnetic and magnetoelectric response of Gd doped nickel ferrite and barium titanate nanocomposites

Abstract: Composites of NiFe2O4 (NFO)–BaTiO3 (BTO) and NiGd0.01Fe1.99O4 (G0.01)–BTO were investigated by x-ray diffraction, magnetization, transmission electron microscopy, magnetocapacitance, and ferroelectric studies. NFO and G0.01 nanoparticles were synthesized by the sol-gel method. The crystallite size of the nanoparticles estimated from the x-ray diffraction patterns is 20–22 nm. The average crystallite sizes of NFO and G0.01 nanoparticles were estimated from the transmission electron micrographs as 26 (1) nm and 22.3 (0.3) nm, respectively. These nanoparticles were encapsulated in a BTO shell, resulting in the formation of nanocomposites. Room temperature magnetization (at 60 kOe) of G0.01 nanoparticles was found to be slightly higher than that of NFO nanoparticles, due to the larger moment of Gd3+ than that of Fe3+. Also, the magnetization of G0.01–BTO is more than that of NFO–BTO nanocomposites. The magnetoelectric effect was observed with a magnetocapacitance value of approximately −10% at 10 kHz in both the composites.