Phase transitions in TbMnO3 manganites

Abstract

X-ray diffraction and magnetic measurements of polycrystalline and nanosize TbMnO 3 manganites have been performed. All the compounds studied crystallize in the orthorhombic crystal structure (space group Pnma) at room temperature. The nanosize manganites were synthesized with a sol-gel method at different (800 and 900°C) temperatures. The average size of synthesized nanoparticles (from 45 to 70 nm) was estimated by using the x-ray diffraction and low-temperature adsorption of argon methods. An information on the evolution of properties of TbMnO 3 with changing grain size, temperature and magnetic field was obtained. The crystal structure parameters of nanospecimens change slightly with changing the nanoparticle size. The peculiarities of magnetic ordering in polycrystalline and nanosize TbMnO 3 were compared. Magnetization and the Nèel temperature corresponding to antiferromagnetic ordering of the Tb 3+ sublattice decrease as the particle size is reduced. The inverse magnetic susceptibility of the nanoparticle samples deviates from the Curie-Weiss law below 50 K, that is connected with the magnetic ordering of the Mn 3+ moments.

Magnetic Properties of Nanoparticle RMnO3 (R=Pr, Nd, and Tb) Compounds

“…The analysis of the diffractograms obtained for the different nano-samples indicates that the fitted structural parameters differ slightly on those for the bulk samples. The data from the X-ray diffraction measurements are listed in Table 1 in [3] and Table 1 in [4].These data confirm that the nano-samples have the similar crystal structure that bulk one. The unit cell volume values reported for the nanoparticle samples are slightly less (about of 1 %) than the value for bulk materials (see Table 23.1).…”

“…The investigated nanoparticle compounds were obtained by a sol-gel technique described in [3,4]. The obtained products were annealed at different temperatures between 800 and 900…”

Effects of holmium substitution on multiferroic properties in Tb0.67Ho0.33MnO3

“…No anomalies related to the magnetic ordering of Mn 3þ moments (as reported for TMO single crystals 9 ) are observed, which is consistent with previous reports for other bulk TMO and is thought to be due to the paramagnetic ordering of larger Tb 3þ moments dominating the AFMordered Mn moments. 25,26 The temperature and frequency dependent real (v 0 ) and complex (v 00 ) parts of the ac susceptibility for the TMO sample are plotted in Figure 2 features to those seen in v dc were observed in the ac susceptibility data. TMO sample exhibits a frequency dependent peak at the Tb 3þ ordering temperature in the v 0 (T) data, and no other significant anomalies are observed.…”

Thermal, Magnetic and Electrical Properties of Multiferroic GdMnO3Nano Particles by a Co-Precipitation Method

“…With a decrease of temperature, there exists an increase in magnetization at 65 K due to the appearance of weak ferromagnetism, which may be contributed by the canting of Mn moments and the polarization of the Gd spins. In the present nano particles, complex magnetic transitions could take place in the vicinity of the transition temperatures of GdMnO 3 , corresponding to the sine wave ordering of Mn 3+ moments and magnetic ordering of Gd 3+ moments, respectively [36]. The Complex magnetic transition of GdMnO 3 nano particles verified by the hysteresis loops of GdMnO 3 nano-particles recorded at different temperatures 20 K, 40 K, 60 K, 80 K and 100 K respectively as shown in Fig.…”