Room temperature magnetic transition in ternary neodymium cobalt germanium 1:2:2 type intermetallics

The magnetocaloric effect (MCE) in theNi2+xMn1-xGa (x = 0.33, 0.36, 0.39), Ni50Mn25In25, Ni54Mn21Ga18In7, Ni53.5Mn21.5Ga16In9, Ni45Co5Mn36.5In13.5 Heusler alloys and in the La0.7BayCa0.3-yMnO3 (y = 0.12, 0.24, 0.3) manganites at the Curie points have been measured by the direct method. For the magnetic field change H = 2 T, the maximal adiabatic temperature change Tad in the Ni2+xMn1-xGa alloys is larger than 0.6 K. For the Ni50Mn25In25 alloy the maximal value of Tad = 1.51 K (for the same magnetic field change H = 2 T) is observed at the magnetic phase transition temperature.

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FERROELECTRIC AND MAGNETIC PROPERTIES OF PEROVSKITE STRUCTURED Bi1-x-yGdxBayFe1-yTiyO3 MAGNETOELECTRIC CERAMICS

Journal of Advanced Dielectrics ◽

10.1142/s2010135x11000318 ◽

2011 ◽

Vol 01 (02) ◽

pp. 257-267 ◽

Cited By ~ 2

Author(s):

RADHESHYAM RAI ◽

IGOR BDIKIN ◽

M. A. VALENTE ◽

ANDREI L. KHOLKIN

Keyword(s):

Magnetic Properties ◽

Room Temperature ◽

Perovskite Phase ◽

Magnetic Transition ◽

Hysteresis Loops ◽

Solid State Reaction Method ◽

All Ceramic ◽

Increasing Temperature ◽

Ferroelectric Transition Temperature ◽

Solution Changes

Ternary solid solutions of BiFeO3 , GdFeO3 and BaTiO3 have been prepared by solid-state reaction method. Dielectric properties of these ceramics have been characterized in the temperature range between room temperature and 673 K and magnetic properties between 5 K and 300 K. For the understanding of the multiferroic property, the relation between the crystal structures, magnetic transition and ferroelectric transitions with increasing temperature have been analyzed. All ceramic samples show single perovskite phase. When Ba content exceeds 0.2 wt%, the sintering ability is weakened and the phase structure of Bi 1-x-y Gd x Ba y Fe 1-y Ti y O 3 (with x = 0.2 and y = 0.1, 0.2, 0.3, 0.4, 0.5) solid solution changes from rhombohedral to tetragonal phase. The maximum ferroelectric transition temperature (Te of this system was in the range 154–165°C with the dielectric constant peak of 6000 for y = 0.5 at 100 kHz. Well-saturated piezoresponse hysteresis loops were observed for all compositions indicating room temperature ferroelectricity. With increasing Ba content (up to 0.3 wt%) the remanent magnetization Mr increased and the coercive magnetic field decreased.

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Observation of magnetic transition around room temperature in the spinel Li[Mn1.96Li0.04]O4 by inelastic neutron scattering

Physica B Condensed Matter ◽

10.1016/j.physb.2004.03.273 ◽

2004 ◽

Vol 350 (1-3) ◽

pp. E991-E993 ◽

Cited By ~ 2

Author(s):

A.J.M Schmets ◽

G.J Kearley ◽

H Mutka ◽

I.M de Schepper

Keyword(s):

Neutron Scattering ◽

Room Temperature ◽

Inelastic Neutron Scattering ◽

Magnetic Transition ◽

Inelastic Neutron

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The Phase Diagram and Exotic Magnetostrictive Behaviors in Spinel Oxide Co(Fe1−xAlx)2O4 System

Materials ◽

10.3390/ma12101685 ◽

2019 ◽

Vol 12 (10) ◽

pp. 1685 ◽

Cited By ~ 3

Author(s):

Chao Zhou ◽

Azhen Zhang ◽

Tieyan Chang ◽

Yusheng Chen ◽

Yin Zhang ◽

...

Keyword(s):

Phase Diagram ◽

Magnetic Susceptibility ◽

Phase Boundary ◽

Room Temperature ◽

Magnetic Transition ◽

Oxide System ◽

Spinel Oxide ◽

System Composition ◽

Temperature Spectra ◽

System 1

We report the magnetic and magnetostrictive behaviors of the pseudobinary ferrimagnetic spinel oxide system (1−x)CoFe2O4–xCoAl2O4 [Co(Fe1−xAlx)2O4], with one end-member being the ferrimagnetic CoFe2O4 and the other end-member being CoAl2O4 that is paramagnetic above 9.8 K. The temperature spectra of magnetization and magnetic susceptibility were employed to detect the magnetic transition temperatures and to determine the phase diagram of this system. Composition dependent and temperature dependent magnetostrictive behaviors reveal an exotic phase boundary that separates two ferrimagnetic states: At room temperature and under small magnetic fields (∼500 Oe), Fe-rich compositions exhibit negative magnetostriction while the Al-rich compositions exhibit positive magnetostriction though the values are small (<10 ppm). Moreover, the compositions around this phase boundary at room temperature (x = 0.35, 0.4, 0.45, 0.5) exhibit near-zero magnetostriction and enhanced magnetic susceptibility, which may be promising in the applications for magnetic cores, current sensors, or magnetic shielding materials.

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Reducibility study of the LaMxFe1−xO3 (M = Ni, Co) perovskites

MRS Proceedings ◽

10.1557/proc-658-gg6.22 ◽

2000 ◽

Vol 658 ◽

Author(s):

C. Estournès ◽

H. Provendier ◽

L. Bedel ◽

C. Petit ◽

A.C. Roger ◽

...

Keyword(s):

Room Temperature ◽

Magnetic Transition ◽

Nickel Content ◽

Product Distribution ◽

Ferromagnetic Behavior ◽

Reducing Atmosphere ◽

Oxidation Of Methane ◽

Reduction Of Iron ◽

Curie Temperatures

ABSTRACTSolid solutions of LaMxFe1−xO3 (with M = Ni and Co) have been used in the Fischer- Tropsch reaction (CO + H2 → Hydrocarbons + CO2) and in the partial oxidation of methane (CH4 + 1/2 O2 → CO + 2 H2). In both catalytic reactions, the active catalyst is reported to be reduced metal particles; their size and their interactions with the support induce large differences in the product distribution.In the nickel system, after total reduction by TPR all catalysts exhibit ferromagnetic behavior at room temperature. In situ magnetization in 1 Tesla on cooling the sample under reducing atmosphere shows one magnetic transition for each sample indicating one Curie temperature. These Curie temperatures are in between those known for bulk nickel and iron and decrease with the initial nickel content of the perovskite. This indicates that nickel is reduced first and induces the reduction of iron, leading to the formation of an alloy.In the cobalt system, in situ magnetization on heating the sample shows a sharp increase of the magnetization only for x = 0.25, 0.40 and 1, corresponding to the formation of metallic cobalt nanoparticles. All other materials present only one increase of the magnetization for temperatures similar to those observed for the second reduction in TPR corresponding to the formation of CoFe alloys.

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Room Temperature Ferromagnetism and Lack of Ferroelectricity in Thin Films of ‘Biferroic’ YbCrO3

MRS Proceedings ◽

10.1557/proc-1161-i07-04 ◽

2009 ◽

Vol 1161 ◽

Cited By ~ 3

Author(s):

Sandeep Nagar ◽

K. V. Rao ◽

Lyubov M. Belova ◽

G. Catalan ◽

J. Hong ◽

...

Keyword(s):

Thin Films ◽

Room Temperature ◽

Room Temperature Ferromagnetism ◽

Magnetic Transition ◽

Ferroelectric Properties ◽

Functional Materials ◽

Spectroscopic Studies ◽

Amorphous Films ◽

New Class ◽

Resistive Material

AbstractSearch for novel multi-functional materials, especially multiferroics, which are ferromagnetic above room temperature and at the same time exhibit a ferroelectric behavior much above room temperature, is an active topic of extensive studies today. Ability to address an entity with an external field, laser beam, and also electric potential is a welcome challenge to develop multifunctional devices enabled by nanoscience. While most of the studies to date have been on various forms of Bi- and Ba based Ferrites, rare earth chromites are a new class of materials which appear to show some promise. However in the powder and bulk form these materials are at best canted antiferromagnetics with the magnetic transition temperatures much below room temperature. In this presentation we show that thin films of YbCrO3 deposited by Pulsed Laser Deposition exhibit robust ferromagnetic properties above room temperature. It is indeed a welcome surprise and a challenge to understand the evolution of above room temperature ferromagnetism in such a thin film. The thin films are amorphous in contrast to the powder and bulk forms which are crystalline. The magnetic properties are those of a soft magnet with low coercivity. We present extensive investigations of the magnetic and ferroelectric properties, and spectroscopic studies using XAS techniques to understand the electronic states of the constituent atoms in this novel Chromite. While the amorphous films are ferromagnetic much above room temperature, we show that any observation of ferroelectric property in these films is an artifact of a leaky highly resistive material.

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