اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe Lowdin orthogonalization and magnetoelectric coupling for noncentrosymmetric ions
113
0
0.0
(
0
)
تأليف
A.S. Moskvin
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The Loewdin orthogonalization procedure being the well-known technique, particularly in quantum chemistry, however, gives rise to novel effects missed in earlier studies. Making use of the technique of irreducible tensorial operators we have developed a regular procedure for account of the orthogonalization effects. For illustration we address the emergence of a specific magnetoelectric coupling for noncentrosymmetric 3d or 4f ions.
قيم البحث
اقرأ أيضاً
How the magnetoelectric coupling actually occurs on a microscopic level in multiferroic BiFeO3 is not well known. By using the high-resolution single crystal neutron diffraction techniques, we have determined the electric polarization of each individ
ual elements of BiFeO3, and concluded that the magnetostrictive coupling suppresses the electric polarization at the Fe site below TN. This negative magnetoelectric coupling appears to outweigh the spin current contributions arising from the cycloid spin structure, which should produce a positive magnetoelectric coupling.
We report the results of direct measurement of remanent hysteresis loops on nanochains of BiFeO$_3$ at room temperature under zero and $sim$20 kOe magnetic field. We noticed a suppression of remanent polarization by nearly $sim$40% under the magnetic
field. The powder neutron diffraction data reveal significant ion displacements under a magnetic field which seems to be the origin of the suppression of polarization. The isolated nanoparticles, comprising the chains, exhibit evolution of ferroelectric domains under dc electric field and complete 180$^o$ switching in switching-spectroscopy piezoresponse force microscopy. They also exhibit stronger ferromagnetism with nearly an order of magnitude higher saturation magnetization than that of the bulk sample. These results show that the nanoscale BiFeO$_3$ exhibits coexistence of ferroelectric and ferromagnetic order and a strong magnetoelectric multiferroic coupling at room temperature comparable to what some of the type-II multiferroics show at a very low temperature.
The Haldane spin-chain compound, Tb2BaNiO5, with two antiferromagnetic transitions, one at T1=63K, and the other at T2=25K, has been recently shown by us to be an exotic multiferroic below T2. Here, we report the results of our investigations of Sr d
oping at the Ba site by magnetization, heat-capacity, magnetoelectric (MDE), and pyrocurrent measurements. An intriguing finding, which we stress, is that the ferroelectricity is lost even for a doping level of 10 atomic percent, though magnetic ordering prevails. The doped specimens however retain significant magnetodielectric behaviour, but with reduced magnitudes and qualitative changes with respect to the behaviour of the parent compound. This implies that ferroelectric order is also crucial for the anomalously large MDE in the parent compound, in addition to the role of 4f single-ion anisotropy.
By combining single crystal x-ray and neutron diffraction, and the magnetodielectric measurements on single crystal Fe4Nb2O9, we present the magnetic structure and the symmetry-allowed magnetoelectric coupling in Fe4Nb2O9. It undergoes an antiferroma
gnetic transition at TN=93 K, followed by a displacive transition at TS=70 K. The temperature-dependent dielectric constant of Fe4Nb2O9 is strongly anisotropic with the first anomaly at 93 K due to the exchange striction as a result of the long range spin order, and the second one at 70 K emanating from the structural phase transition primarily driven by the O atomic displacements. Magneticfield induced magnetoelectric coupling was observed in single crystal Fe4Nb2O9 and is compatible with the solved magnetic structure that is characteristic of antiferromagnetically arranged ferromagnetic chains in the honeycomb plane. We propose that such magnetic symmetry should be immune to external magnetic fields to some extent favored by the freedom of rotation of moments in the honeycomb plane, laying out a promising system to control the magnetoelectric properties by magnetic fields.
The transverse and longitudinal magnetoelectric susceptibilities (MES) were quantitatively determined for (001) heteroepitaxial BiFeO$_{3}$-CoFe$_{2}$O$_{4}$ nanostructures. Both of these MES values were sharply enhanced at magnetic fields below 6 kO
e and revealed asymmetric lineshapes with respect to the dc magnetic field, demonstrating the strain-induced magnetoelectric effect. The maximum transverse MES, which reached as high as $sim$60 mV/cm Oe, was about five times larger than the longitudinal MES. This observation signifies that transverse magnetostriction of the CoFe$_{2}$O$_{4}$ nanopillars is enhanced more than the bulk value due to preferred magnetic domain alignment along the [001] direction coming from compressive, heteroepitaxial strain.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
