Experimental investigation of the effect of thermal hysteresis in first order material MnFe(P,As) applied in an AMR device

2014 ◽  
Vol 37 ◽  
pp. 303-306 ◽  
Author(s):  
L. von Moos ◽  
K.K. Nielsen ◽  
K. Engelbrecht ◽  
C.R.H. Bahl
Keyword(s):  
Experimental Investigation ◽  
Thermal Hysteresis ◽  
First Order

scholarly journals Reversibility of the Magnetocaloric Effect in the Bean-Rodbell Model

2021 ◽  
Vol 7 (5) ◽  
pp. 60
Author(s):  
Luis M. Moreno-Ramírez ◽  
Victorino Franco
Keyword(s):  
Magnetic Field ◽  
Thermal Hysteresis ◽  
Entropy Change ◽  
Second Order ◽  
Zero Field ◽  
First Order ◽  
Magnetic Field Change ◽  
Magnetocaloric Materials ◽  
Moderate Magnetic Field ◽  
The Magnetic Field

The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the η parameter (η<1 for second-order and η>1 for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (TEC), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of TEC is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with η≈1.3−1.8 have better TEC than those corresponding to stronger first-order transitions and even second-order ones.

First-order reversal curve analysis of spin-transition thermal hysteresis in terms of physical-parameter distributions and their correlations

2005 ◽  
Vol 71 (1) ◽  
Author(s):  
Radu Tanasa ◽  
Cristian Enachescu ◽  
Alexandru Stancu ◽  
Jorge Linares ◽  
Epiphane Codjovi ◽  
...  
Keyword(s):  
Physical Parameter ◽  
Thermal Hysteresis ◽  
Spin Transition ◽  
Curve Analysis ◽  
First Order ◽  
Parameter Distributions

First-order reversal curves analysis of rate-dependent hysteresis: The example of light-induced thermal hysteresis in a spin-crossover solid

2005 ◽  
Vol 72 (5) ◽  
Author(s):  
Cristian Enachescu ◽  
Radu Tanasa ◽  
Alexandru Stancu ◽  
Francois Varret ◽  
Jorge Linares ◽  
...  
Keyword(s):  
Spin Crossover ◽  
Thermal Hysteresis ◽  
First Order ◽  
Rate Dependent

Hypersonic and Dielectric Studies of Relaxor Ferroelectric Single Crystal

1999 ◽  
Vol 604 ◽  
Author(s):  
Chi-Shun Tu ◽  
V.H. Schmiidt ◽  
C.-H. Yeh ◽  
L.-F. Chen ◽  
C.-L. Tsai
Keyword(s):  
Phase Transition ◽  
Dielectric Permittivity ◽  
Single Crystal ◽  
Thermal Hysteresis ◽  
Relaxor Ferroelectric ◽  
Dipolar Relaxation ◽  
First Order ◽  
Dielectric Data ◽  
Scattering Spectra ◽  
Ferroelectric Single Crystal

AbstractBoth the longitudinal (LA) Brillouin back-scattering spectra and dielectric permittivity along the [001] direction have been measured as a function of temperature for a relaxor ferroelectric single crystal (PbMg1/3Nb2/3O3)0.68(PbTiO3)0.32 (PMN-32%PT). A sharp ferroelectric phase transition (which is associated with a Landau-Khalatnikov-like phonon damping maximum) was observed near 445 K. As temperature increases, a diffuse phase transition was detected near 280 K. In addition, the nature of the thermal hysteresis for the dielectric permittivity confirms that these transitions (near 280 and 445 K for heating procedure) are diffuse first-order and first-order, It respectively. The dielectric data prove the existence of an electric dipolar relaxation process below 300 K.

Ultrasonic Relaxation in Phase Transition Region in Ferroelectric Semiconductors of Sn2P2S6 Family

2012 ◽  
Vol 184 ◽  
pp. 345-350
Author(s):  
Vytautas Samulionis ◽  
Juras Banys ◽  
Yulian Vysochanskii
Keyword(s):  
Phase Transition ◽  
Ultrasonic Velocity ◽  
Thermal Hysteresis ◽  
Ultrasonic Attenuation ◽  
Landau Theory ◽  
Velocity Change ◽  
First Order ◽  
Temperature Range ◽  
Large Hysteresis ◽  
Relative Change

The paper presents recent results of ultrasonic investigation of Sn2P2S6 family ferroelectric crystals and their solid solutions in the temperature range 100-300 K. It was shown that in Sn2P2(S,Se)6 crystals the critical ultrasonic velocity slowing down for longitudinal waves propagating along main crystallographic directions is quite sharp and large. The relative change of longitudinal ultrasonic velocity along z-axis at the phase transition gradually increased from 10 % in pure Sn2P2S6 till 25 % for sample with 0.4 content of Se. Such large velocity change causes the large ultrasonic attenuation anomaly. The increase of relaxation time: τ=τ0/(TC-T) leads to the increase of attenuation. Prefactor τ0 was shown to be very small and the critical attenuation anomaly arises in the narrow temperature range close to phase transition. In the 0.4 Se sample the phase transition is of the first order because small thermal hysteresis exists. The ultrasonic velocity behaviour in the ferroelectric phase was described using Landau theory and free energy expansion including sixth order terms. For (Sn,Pb)2P2S6 system the critical ultrasonic anomalies were smaller and the phase transition temperature substantially decreased (for 0.45 Pb sample the phase transition point was at Tc =140 K). The ultrasonic anomalies at phase transition in (PbxSn1-x)2P2S6 have large hysteresis showing that transition is of the first order, far from the critical point.

scholarly journals Analysis of first order reversal curves in the thermal hysteresis of spin-crossover nanoparticles within the mechanoelastic model

2015 ◽  
Vol 117 (17) ◽  
pp. 17B307 ◽  
Author(s):  
Laurentiu Stoleriu ◽  
Alexandru Stancu ◽  
Pradip Chakraborty ◽  
Andreas Hauser ◽  
Cristian Enachescu
Keyword(s):  
Spin Crossover ◽  
Thermal Hysteresis ◽  
First Order

scholarly journals Evidence of Photo-Thermal Effects on the First-Order Thermo-Induced Spin Transition of [{Fe(NCSe)(py)2}2(m-bpypz)] Spin-Crossover Material

2019 ◽  
Vol 5 (2) ◽  
pp. 21 ◽  
Author(s):  
Kamel Boukheddaden ◽  
Houcem Fourati ◽  
Yogendra Singh ◽  
Guillaume Chastanet
Keyword(s):  
Thermal Effects ◽  
Spin Crossover ◽  
Evolution Equations ◽  
Thermal Hysteresis ◽  
Magnetic Measurements ◽  
Equations Of Motion ◽  
Spin Transition ◽  
Thermal Bath ◽  
Trapping Region ◽  
First Order

We have investigated by means of optical microscopy and magnetic measurements the first-order thermal spin transition of the [{Fe(NCSe)(py)2}2(m-bpypz)] spin-crossover compound under various shining intensities, far from the light-induced spin-state trapping region. We found evidence of photo-heating effects on the thermally-induced hysteretic response of this spin-crossover material, thus causing the shift of the thermal hysteresis to lower temperature regions. The experimental results are discussed in terms of the apparent crystal temperature and are analyzed theoretically using two evolution equations of motion, written on the high-spin (HS) fraction and heat balance between the crystal and the thermal bath. A very good qualitative agreement was found between experiment and theory in the stationary regime, explaining the experimental observations well and identifying the key factors governing these photo-thermal effects.

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