Search results for "Ferro"

Dielectric properties of Pb(Fe1/2Ta1/2)O3ceramics over 70–300 K temperature range

2011

The studies of dielectric response in ferromagnetic lead ferrotantalate Pb(Fe1/2Ta1/2)O3 are reported over a wide range of temperature under the applied bias field. The features of dielectric nonlinearity deduced from behaviour of reverse e'(E=) curves at different temperatures, including regions of ferroelectric phase transition and vicinity of the Neel point, are examined. Obtained results indicate a substantial broadening of the ferroelectric phase transition. The results are discussed with respect to effects of ferroelectric ordering in relaxor materials of such kind.

Magnetic and structural phase transitions by annealing in tetragonal and cubic Mn3Ga thin films

2021

Abstract Thermal Annealing is a simple and powerful tool to improve the crystallinity in general or promote the functionality for peculiar purposes, ultimately leading to metastable states with lower energy. We report the annealing effect focusing primarily on the structural and magnetic properties of two different Mn3Ga thin films. One is the D022 tetragonal ferrimagnetic phase Mn3Ga, and the other is the disordered-L12 cubic antiferromagnetic phase Mn3Ga. They were grown by RF/DC magnetron sputtering method on MgO substrate. After deposition, the thin films were annealed at various temperatures (200, 300, 400, 500, and 600 °C) and Ar pressures (10−3, 10−1, and 103 Torr). We find that the …

Reversive Dielectric Response in xPZN-(1 − x) PSN Ceramics

2006

The effects of bias fields E= on dielectric response of xPbZn1/3Nb2/3O3-(1 − x)PbSc1/2 Nb1/2O3 ferroelectric solid solutions of x = 0, 0.05, 0.2, and 0.5 studied at temperatures of diffused phase transitions are reported. The thermal interval of the existence of a relaxor phase in the system is found to shrink with the concentration of PbZn1/3Nb2/3O3. The change of the ratio of zinc-lead and scandium-lead niobate components is deduced to change the features of the transition to polarised state from first-order to second-order transition.

Phase State and Structure of Ferroelectric Ceramics under Irradiation

1997

PHASE TRANSITIONS IN THE PLZT x/85/15 SOLID SOLUTIONS

2008

ABSTRACT Role of a La on the nature of phase transition in the PLZT x/85/15 is compared with the PLZT compositions of lower Zr/Ti ratio. Thermal dependence of the dielectric permittivity, thermal expansion and elastic modulus reveal sequential transfer from macroscopic ferroelectric to antiferroelectric and nonpolar state, if La concentration is increased. Diffused, from frequency independent thermal dependence of dielectric permittivity for compositions in certain La concentration range above 4 at% coexist with the well expressed phase transition between paraelectric and antiferroelectric phases.

Broadband dielectric spectroscopy of PbMg1/3Nb2/3O3–PbSc1/2Nb1/2O3 ceramics

2010

Abstract Broadband dielectric spectroscopy results of various ordered and disordered (1 − x)Pb(Mg1/3Nb2/3)O3–(x)Pb(Sc1/2Nb1/2)O3 (PMN–PSN) ceramics are investigated in the temperature range from 80 K to 300 K and frequency range from 20 Hz to 2 THz. Dielectric dispersion is very broad and in the ferroelectrics case (x = 1, 0.95) consists of two parts: low-frequency part caused by ferroelectric domains and higher frequency part caused by soft mode. The relaxational soft mode exhibits pronounced softening close to phase transition temperature, as it is typical for order–disorder phase transitions. By substituting Sc3+ by Mg2+ in PMN–PSN ceramics relaxation slows down, and for relaxors (x = 0.…

Radiation effects in transparent ferroelectric ceramics

1997

Radiation of different types ((gamma) -rays, electrons, neutrons) and fluence has been used to study the defect processes as well as the change of physical parameters in PLZT X/65/35 (X equals 4.5 - 11 at.%) and PbSc 0.5 Nb 0.5 O 3 (PSN) ceramics and to evaluate critical irradiation conditions. Effects on optical (extinction) spectra and dielectric characteristics (polarization, thermal and frequency dependences of dielectric permittivity (epsilon) and losses), dependent on composition and state of phase and polarization have been analyzed by means of annealing in isochronic and prolonged time regimes. A gradual shift of extinction edge to longer wavelengths, reduction of polarization and (…

Size effects of static and dynamic polarization in ferroelectric thin film multilayers

2001

Abstract A thermodynamic theory for the calculation of static and dynamic polarization profiles of ferroelectric thin film multilayers is developed. The free energy functional is written down using a multilayer model in which c-domain layers of the ferroelectric material alternate with a-domain layers of a second ferroelectric materials. We assume that the interfaces are perfectly sharp and that the polarization at these boundaries is zero. The equilibrium polarization profile, its temperature and thickness dependencies were determined from the solutions of the Euler-Lagrange equations. A thickness induced ferroelectric phase transition is shown to exist and its transition temperature and c…

Gradual phase transition from ferromagnetic tetragonal to antiferromagnetic cubic states in Mn Ga (1.80 ≤ x ≤ 3.03) thin films

2019

Abstract The structural, magnetic, and electronic properties of MnxGa thin films are investigated as varying the Mn composition (1.80 ≤ x ≤ 3.03). The variation of x in MnxGa films dramatically changes the crystal structure as well as the magnetic properties. With increasing x, we observe the gradual phase transition from a ferromagnetic tetragonal state to an antiferromagnetic cubic state. The structural characterization reveals that the D022 tetragonal structure of Mn2Ga is slowly transformed to the L12 cubic structure of Mn3Ga. Two phases coexist around x = 2.4. The magnetization is systematically reduced as x increases, ending to an antiferromagnetic state of cubic Mn3Ga, and the electr…

Broadband Dielectric Spectroscopy of Ferroelectric Phase Transitions in PbSc1/2Nb1/2O3Ordered Ceramics

2008

Broadband dielectric spectroscopy of PbSc 1/2 Nb 1/2 O 3 (PSN) ordered ceramics are reported within the range of 20 Hz ≤ ν ≤ 2 THz in 80 K ≤ T ≤ 300 K temperatures. Spectrally very broad dielectric dispersion consisting of two parts − at lower frequencies, ferroelectric domains cause a dispersion and at higher frequencies, higher temperatures the relaxation soft mode is responsible for the dispersion. The relaxation soft mode exhibit pronounced hardening on cooling, whilst the ferroelectric phase transition is connected with an abrupt freezing and rise of polar nanoregions into ferroelectric domains.