Coexistence of considerable inter-particle interactions and spin-glass behavior in La0.7Ca0.3MnO3 nanoparticles

Abstract

We have studied the magnetic and spin-glass (SG) properties of La0.7Ca0.3MnO3 single-crystalline nanoparticles, which were prepared by the mechanical milling method with different milling times (tm). Analyzing the susceptibility data in the paramagnetic region indicates both ferromagnetic (FM) and anti-FM interactions coexisting in nanoparticles. Additionally, there is a peak associated with the freezing temperature (Tf) appearing on the real part curve of the ac susceptibility, χ′(T). The Tf value increases with increasing frequency as expected for SG systems. The SG behavior was also checked by using the criterion parameter c = ΔTf/TfΔ(log10f), and the power law τ = τ0(T/Tg − 1)−zν. The obtained values of c ≈ 5 × 10−2, τ0 ≈ 10−5 s and zν ≈ 2–3 are consistent with those expected for SG-like systems, suggesting an existence of a SG phase transition at Tg below Tf, which decreases with decreasing ⟨D⟩. Basing on ln(f) versus Tf data, and the Néel-Arrhenius model [ln(f) = ln(f0) - Ea/kBT] and Vogel–Fulcher law [ln(f) = ln(f0) - Ea/kB(T - T0)], the Larmor frequency (f0), activation energy (Ea) and effective temperature (T0) for the samples with different ⟨D⟩ were determined. Obtained results indicate the existence a strong interaction between nanoparticles.

Spin glass transition of single-crystalline TmFe2O4− δ

“…where τ is the characteristic relaxation time that is equal to 1/f , τ 0 is the microscopic relaxation time which indicates a spin flip time of an individual magnetic moment or a magnetic cluster, z is the dynamical exponent, and v is the critical exponent for the magnetic correlation length. In the present case, the best fit of equation ( 2) to the experimental data, as shown in the inset of figure 3(a), yields that zv = 8.68(8), T g = 186.2 K and τ 0 = ∼10 −13.66 (5) s. Considering the fact that zv values previously reported for spin glasses including alloys, sulfides and oxides lie in a range of 4-13 [40], the present value zv = 8.68 (8) suggests that the magnetic structure at low temperatures can be categorized into a spin glass state. In addition to the zv value, the value of τ 0 , i.e., 10 −13.66 (5) s is also reasonable for the typical spin glasses [41,42].…”

Effect of Al3+ substitution on the structural, magnetic, and electric properties in multiferroic Bi2Fe4O9 ceramics

“…where T g is the SG transition temperature (which is equivalent to the freezing temperature in the limit of τ-1), and zν and τ 0 are the critical exponents and characteristic time constant, respectively [27]. The best fit to the above equation, as shown in inset of Fig.…”

Structure and Magnetic Properties of Nd0.88MnO3 Films Grown on SrTiO3 (100) Substrates by Liquid-Injection MOCVD

“…A clear bifurcation of the FC and ZFC with a lambda shaped-like has been observed. These phenomena are collectively treated before as spin-glass system (SG) behaviors, where Tirr is generally close to but slightly below Tf [33][34][35]. Also, although in the cluster glass (CG) systems, Tirr is usually higher than Tf, [36,37].…”