Broadband Electron Spin Resonance Study in a Sr2FeMoO6 Double Perovskite

Contrasting Magnetic Characteristics of Disordered Nd0.5Ba0.5Mn0.5Fe0.5O3-δ/2 and 112-Type Ordered NdBaMnFeO6-δ Perovskites

The magnetic properties of disordered Nd0.5Ba0.5Mn0.5Fe0.5O3-δ/2 and ordered NdBaMnFeO6-δ perovskites were investigated through temperature- and field-dependent DC-magnetization measurements. The temperature dependence of magnetic susceptibilities revealed that antiferromagnetic ordering occurs at temperatures below 185 K for the disordered Nd0.5Ba0.5Mn0.5Fe0.5O3-δ/2 sample, whereas the ordered NdBaMnFeO6-δ perovskite exhibited a paramagnetic state throughout the entire temperature range examined. Notably, the disordered sample exhibited a glassy state, even at room temperature, which transformed into an antiferromagnetic state under higher applied magnetic fields. The magnetic ordering in the disordered Nd0.5Ba0.5Mn0.5Fe0.5O3-δ/2 perovskite and the magnetic-disordering state in the structurally ordered NdBaMnFeO6-δ perovskite could be attributed to the alteration of the oxidation state of Mn.

Study of biopolymer encapsulated Eu doped Fe3O4 nanoparticles for magnetic hyperthermia application

An exciting prospect in the field of magnetic fluid hyperthermia (MFH) has been the integration of noble rare earth elements (Eu) with biopolymers (chitosan/dextran) that have optimum structures to tune specific effects on magnetic nanoparticles (NPs). However, the heating efficiency of MNPs is primarily influenced by their magnetization, size distribution, magnetic anisotropy, dipolar interaction, amplitude, and frequency of the applied field, the MNPs with high heating efficiency are still challenging. In this study, a comprehensive experimental analysis has been conducted on single-domain magnetic nanoparticles (SDMNPs) for evaluating effective anisotropy, assessing the impact of particle-intrinsic factors and experimental conditions on self-heating efficiency in both noninteracting and interacting systems, with a particular focus on the dipolar interaction effect. The study successfully reconciles conflicting findings on the interaction effects in the agglomeration and less agglomerated arrangements for MFH applications. The results suggest that effective control of dipolar interactions can be achieved by encapsulating Chitosan/Dextran in the synthesized MNPs. The lower dipolar interactions successfully tune the self-heating efficiency and hold promise as potential candidates for MFH applications.

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

To maximize heat release from immobilized nanoparticles (NPs), a detailed understanding of the controlled dipolar interaction is essential for challenging magnetic hyperthermia (MH) therapies. To design optimal MH experiments, it is necessary to precisely determine magnetic states impacted by the inevitable concurrence of magnetic interactions under a common experimental form. In this work, we describe how the presence of dipolar interaction significantly alters the heating mechanism of host materials when NPs are embedded in them for MH applications. The concentration of the NPs and the intensity of their interaction can profoundly impact the amplitude and shape of the heating curves of the host material. The heating capability of interacting NPs might be enhanced or diminished, depending on their concentration within the host material. We propose chitosan- and dextran-coated Gd-doped Fe3O4 NPs directing dipole interactions effective for the linear regime to enlighten the pragmatic trends. The outcomes of our study may have substantial implications for cancer therapy and could inspire novel approaches for maximizing the effectiveness of MH.

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

An exciting prospect in the field of magnetic fluid hyperthermia (MFH) has been the integration of noble rare earth elements with biopolymers (chitosan/dextran) that have optimum structures to tune specific effects on magnetic nanoparticles (MNPs). Remarkably, it has been demonstrated that dipole-dipole interactions have a significant influence on nanoparticle dynamics. In this article, we present an exhaustive scrutiny of dipolar interactions and how this affects the efficiency of MFH applications. In particular, we prepare chitosan and dextran-coated Tb-doped MNPs and study whether it is possible to increase the heat released by controlling the dipole-dipole interactions. It has been indicated that even moderate control of agglomeration may substantially impact the structure and magnetization dynamics of the system. Besides estimating the specific loss power value, our findings provide a deep insight into the relaxation mechanisms and bring to light how to tune the self-heating efficacy towards magnetic hyperthermia.

Electron Spin Decoherence Dynamics in Magnetic Manganese Hybrid Organic-Inorganic Crystals: The Effect of Lattice Dimensionality

Organic-inorganic metal hybrids with their tailorable lattice dimensionality and intrinsic spin-splitting properties are interesting material platforms for spintronic applications. While the spin decoherence process is extensively studied in lead- and tin-based hybrids, these systems generally show short spin decoherence lifetimes, and their correlation with the lattice framework is still not well-understood. Herein, we synthesized magnetic manganese hybrid single crystals of (4-fluorobenzylamine)2MnCl4, ((R)-3-fluoropyrrolidinium)MnCl3, and (pyrrolidinium)2MnCl4, which represent a change in lattice dimensionality from 2D and 1D to 0D, and studied their spin decoherence processes using continuous-wave electron spin resonance spectroscopy. All manganese hybrids exhibit nanosecond-scale spin decoherence time τ2 dominated by the symmetry-directed spin exchange interaction strengths of Mn2+-Mn2+ pairs, which is much longer than lead- and tin-based metal hybrids. In contrast to the similar temperature variation laws of τ2 in 2D and 0D structures, which first increase and gradually drop afterward, the 1D structure presents a monotonous rise of τ2 with the temperatures, indicating the strong correlation of spin decoherence with the lattice rigidity of the inorganic framework. This is also rationalized on the basis that the spin decoherence is governed by the competitive contributions from motional narrowing (prolonging the τ2) and electron-phonon coupling interaction (shortening the τ2), both of which are thermally activated, with the difference that the former is more pronounced in rigid crystalline lattices.

Role of site selective substitution, magnetic parameter tuning, and self heating in magnetic hyperthermia application: Eu-doped magnetite nanoparticles

Various researchers have provided considerable insight into the fundamental mechanisms behind the power absorption of single-domain magnetic nanoparticles (MNPs) in magnetic hyperthermia applications. However, the role of all parameters pertinent to magnetic relaxation continues to be debated. Herein, to explore the role of magnetic anisotropy with the site selective substitution related to magnetic relaxation has generally been missing, which is critically essential in respective of hyperthermia treatment. Our study unravels contradictory results of rare earth (RE) interaction effects in ferrite to that of recently reported literature. Despite this, rare earth atoms have unique f-block properties, which significantly impact the magnetic anisotropy as well as the relaxation mechanism. Here, we use appropriate Eu doping concentration in magnetite and analyze its effect on the matrix. Furthermore, a positive SAR can effectively reduce the relative dose assigned to a patient to a minimal level. This study indicates that the introduction of Eu ion positively influenced the heating efficiency of the examined magnetite systems.

Electron spin resonance studies of (La0.6Ln0.4)0.67Ca0.33MnO3 (Ln = La, Pr, Nd and Sm) nanoparticles at different temperatures

In this work, (La0.6Ln0.4)0.67Ca0.33MnO3 (Ln = La, Pr, Nd and Sm) nanoparticles (NPs) synthesized by sol-gel process were investigated by electron spin resonance (ESR) in the temperature range 100–330 K. At the high temperature the ESR signals of La0.67Ca0.33MnO3 (LCMO) NPs only consist of a single peak with Landé g factor of 2.0. This signal is contributed from the paramagnetic (PM) Mn ions in the LCMO NPs. With decreasing the temperature the PM resonance line is split into two resonance lines, one is ferromagnetic (FM) resonance line shifting towards low field while the other is antiferromagnetic (AFM) resonance line moving to a high field. The resonance peak-to-peak spectra linewidth, increases monotonically with decreasing the temperature owing to the strong double exchange interactions below the Curie temperature (T C). Resonance field is almost temperature independent in the PM phase whereas it drops fast at temperature below T C. Consequently, the Landé g factor in the PM region is very close to 2.0 whereas in the range of 2.17–2.47 under FM state due to the strong FM interactions. For the Pr (Nd)-doped LCMO NPs below T C, their g values are in the range of 2.04–2.18 due to the substantial reduction of the FM interactions caused by the Pr (Nd)-doping at La-site. The g values of the Sm-doped LCMO NPs exhibit a slight fluctuation around 1.88 (but smaller than 2.0) within the measured temperature due to the existence of weak magnetic interactions under the PM states.