Magnetic, electron magnetic resonance and optical studies of Pr_0.7Pb_0.3MnO₃nanoparticles

Abstract

In this paper we present the preparation and physical property studies on Pr0.7Pb0.3MnO3 (PPMO) nanoparticles with an average grain size of 5 nm. We find from SQUID magnetometry measurements that the Curie temperature (TC) remains unaltered at 205 K with decrease in the particle size down to 5 nm in comparison with bulk TC (200 K). From electron magnetic resonance (EMR) measurements, it is found that PPMO nanoparticles are more homogeneous than bulk PPMO. Only one EMR signal is observed down to 4 K in PPMO with an average particle size of 5 nm in contrast to the two EMR signal behaviour observed in bulk PPMO (200–240 K). The origin of the two EMR signals in the bulk was attributed to possible phase separation (Padmanabhan B et al 2007 Physica B 398 107). Such a phase separation is therefore concluded to be absent in nano-PPMO. In addition, temperature-dependent optical phonon measurements performed on 5 nm PPMO nanoparticles indicate the insulator–metal transition TMI = 230 K, which is nearly the same as that of the bulk sample (TMI = 235 K).

2D correlations in the van der Waals ferromagnet CrBr3 using high frequency electron spin resonance spectroscopy

“…Due to the high sensitivity of ESR spectroscopy compared to conventional magnetometers, this technique is able to pick up ferromagnetic correlations much above TC as reflected through the appearance of multiple signals even above 32 K, consistent with the previous reports [13]. Numerous ESR signals are typically observed in ferromagnetic compounds due to magnetocrystalline anisotropy, magnetic inhomogeneity and magnetic phase separation [22][23][24][25][26][27]. The g-value is seen to increase at a somewhat exponential rate as temperature is lowered from g = 2.016 at T = 200 K to g = 2.082 at T = 4 K beginning at T = 40 K (not shown).…”

Realizing the ‘hindered charge ordered phase’ in nanoscale charge ordered manganites: magnetization, magneto-transport and EPR investigations

“…No indication of a CO peak at around 250 K is seen, and a sudden rise in magnetization at around 150 K indicates the onset of ferromagnetic phase. The peak at 50 K indicates the 'blocking temperature (T b )' [28]. Field cooled cooling (FCC) and field cooled warming (FCW) measurements have been performed on NCMO 10 at 1 T and the results are shown in the same figure.…”

Electron magnetic resonance in interacting ferromagnetic-metal nanoparticle systems: experiment and numerical simulation

“…In spite of intensive studies [10][11][12], the EMR in ferromagnetic-metal nanoparticle systems is poorly understood. The magnetic behavior and dynamics of magnetization in nanoparticle systems are dependent both on single-particle properties, such as magnetocrystalline or shape anisotropies of a particle [13][14][15][16][17], and on interparticle interactions [18,19]. For magnetically isolated particles with negligible interaction, one needs to consider only single-particle properties.…”