9 research outputs found
Tuning a sign of magnetoelectric coupling in paramagnetic NH2(CH3)2Al1-xCrx(SO4)*6H2O crystals by metal ion substitution
Hybrid organometallic systems offer a wide range of functionalities,
including magnetoelectric interactions. However, the ability to design
on-demand ME coupling remains challenging despite a variety of host-guest
configurations and ME phases coexistence possibilities. Here, we report the
effect of metal-ion substitution on the magnetic and electric properties in the
paramagnetic ferroelectric DMAAS crystals. Doing so we are able to induce and
even tune a sign of the ME interactions in the paramagnetic ferroelectric
state. Both studied samples with 6.5% and 20% of Cr become paramagnetic,
contrary to the initial diamagnetic compound. Due to the isomorphous
substitution with Cr the ferroelectric phase transition temperature increases
nonlinearly, with the shift being larger for the sample with Cr content of
6.5%. A magnetic field applied along the polar c axis increases
ferroelectricity for this sample and shifts Tc to higher values, while inverse
effects are observed for sample containing 20% of Cr. The ME coupling
coefficient of 1.7ns/m found for a crystal with 20% of Cr is among the highest
reported up to now. The observed sign change of ME coupling coefficient with a
small change in Cr content paves the way for ME coupling engineering.Comment: 7 pages, 6 figures. New Organometallic Magnetoelectric and
Ferroelectric compoun
Tuning a sign of magnetoelectric coupling in paramagnetic NH2(CH3)(2)Al1-xCrx(SO4)(2) x 6H(2)O crystals by metal ion substitution
Hybrid organometallic systems offer a wide range of functionalities, including magnetoelectric (ME) interactions. However, the ability to design on-demand ME coupling remains challenging despite a variety of host-guest configurations and ME phases coexistence possibilities. Here, we report the effect of metal-ion substitution on the magnetic and electric properties in the paramagnetic ferroelectric NH2(CH3)(2)Al1-xCrx(SO4)(2) x 6H(2)O. Doing so we are able to induce and even tune a sign of the ME interactions, in the paramagnetic ferroelectric (FE) state. Both studied samples with x = 0.065 and x = 0.2 become paramagnetic, contrary to the initial diamagnetic compound. Due to the isomorphous substitution with Cr the ferroelectric phase transition temperature (T-c) increases nonlinearly, with the shift being larger for the 6.5% of Cr. A magnetic field applied along the polar c axis increases ferroelectricity for the x = 0.065 sample and shifts Tc to higher values, while inverse effects are observed for x = 0.2. The ME coupling coefficient alpha(ME) = 1.7 ns/m found for a crystal with Cr content of x = 0.2 is among the highest reported up to now. The observed sign change of aME with a small change in Cr content paves the way for ME coupling engineering
Dielectric and Birefringent Properties of [(CH)NH]CdCuCl Solid Solutions in the Region of Their Phase Transitions
On the basis of the optical and dielectric investigations of [(CH)NH]CdCuCl solid solutions the existence of phase transitions at T=175 K and T=117.5 K was confirmed. Both phase transitions were found to be shifted toward lower temperatures with respect to the corresponding transitions in the "host" [(CH)NH]CdCl crystals. It was found that the proton conductivity in [(CH)NH ]CdCuCl crystals is realized through the Grotthus mechanism. The investigations of the birefringent properties confirmed existence of the structural changes at T=320 K connected with the complex co-operative effect involving weakening of the hydrogen bonds and modification of the Jahn-Teller distortion with temperature
Chromium doped NH2(CH3)2Ga(SO4)2 × 6H2O crystal – representative of a new family of magnetoelectric materials
The paper is devoted to the detailed study of electric and magnetic properties and magnetoelectric interactions in NH _2 (CH _3 ) _2 Ga(SO _4 ) _2 × 6H _2 O crystals doped with chromium—DMAGaS:Cr. The temperature dependence of the specific heat revealed clear evidence of a series of phase transitions related to the electric dipoles ordering. The different types of the DMA cation ordering in the structure of DMAGaS:Cr were evidenced in the temperature evolution of the EPR spectra. In addition, a considerable magnetoelectric coupling was demonstrated within the paramagnetic and ferroelectric phase of DMAGaS:Cr crystal. In the narrow temperature range in the vicinity of the Curie point, this crystal was found to possess the largest values of the coefficient of ME interaction as well as the largest magnetodielectric effect within the family of ferroics with organic cation. The model describing the ME effect was proposed. The magnetic field through the magnetostriction effect changes the level of the local lattice deformations caused by metal ion substitution. The applied magnetic field changes Cr-Cr distances and modifies the hydrogen bonds and process of DMA group ordering, affecting spontaneous polarization
Phase Transitions and Fundamental Ferroelectric Dispersion in DMAAl Crystals
This paper presents the results of investigations of the temperature dependence of heat capacity and dielectric dispersion in the vicinity of ferroelectric-ferroelastic phase transition of dimethylammonium metal sulphate hexahydrate crystals DMAAl. In particular, it is shown that the isomorphous substitution of metal ion noticeably changes the temperature of phase transition and parameters of the fundamental ferroelectric dispersion observed around . These changes are explained in terms of clusters sizes and dynamics in the framework of order-disorder type phase transition mechanism