Transverse spin relaxation and magnetic correlation in Pr1−x Ca x MnO3: Influence of particle size variation and chemical doping

Abstract

The short ranged magnetic correlations and dynamics of hole doped Pr1–xCaxMnO3 (0.33 < x < 0.5) of different crystallite sizes have been investigated using electron spin resonance spectroscopy. The major contribution to the temperature dependence of paramagnetic line-width is attributed to the spin-lattice relaxation dominated by thermally activated hopping of small polarons with the typical activation energy of 20–50 meV. Irrespective of the crystallite size and dopant concentration, the transverse spin relaxation time (t2) follows a universal scaling behaviour of the type t2∼(T/T0)n in the paramagnetic regime, where T0 and n are the scaling parameters. Using the temperature dependence of t2, we construct a phase diagram which shows that near half-doping, the magnetic correlations associated with charge ordering not only survives even down to the crystallite size of 22 nm but is also actually enhanced. We conclude that the eventual suppression of charge ordering with reduction in the particle size is possibly more to do with the greater influence of chemical disorder than any intrinsic effect.

RETRACTED ARTICLE: A comprehensive scrutiny to controlled dipolar interactions to intensify the self-heating efficiency of biopolymer encapsulated Tb doped magnetite nanoparticles

“…Additionally, the small value of g and H pp signifies the strong super-exchange interaction. After this, the lower g and H pp values for dextran and chitosan-coated MNPs illustrate a stochastic arrangement of magnetic moments with enhancing particle size 39 – 41 . As enumerated in Table 2 , the listed lower spin–spin relaxation time (τ 1 ) for coated samples rather than the uncoated one can lead to an ability of higher power dissipation of the synthesized MNPs 42 .…”

Antiferromagnetic rare region effect in Pr0.5Ca0.5MnO3

“…A comparison of the LF/HF signals and PM signals shows that the fraction of spins contributing to the LF and HF resonances are ≤ 1.7% and ≤ 1.65%, respectively, which are slightly higher than the corresponding bulk sample. The mismatch of the anomalies in the macroscopic susceptibility and the LF/HF signal parameters can be attributed to the increased FM correlation in the main signal due to reduction in grain size [48] as well as the distribution of the grain size in the nanocrystalline sample.…”

Influence of Controlled Dipolar Interaction for Polymer-Coated Gd-Doped Magnetite Nanoparticles toward Magnetic Hyperthermia Application

“…Furthermore, the small value of g and H pp signifies the strong superexchange interaction. Henceforward, the lower g and H pp values for dextran- and chitosan-coated Gd-doped MNPs suggest a random alignment of magnetic moments with improving particle size. − …”