This review is focused on describing state-of-the-art synthetic routes for the preparation of magnetic nanoparticles useful for biomedical applications. In addition to this topic, we have also described in some detail some of the possible applications of magnetic nanoparticles in the field of biomedicine with special emphasis on showing the benefits of using nanoparticles. Finally, we have addressed some relevant findings on the importance of having well-defined synthetic routes to produce materials not only with similar physical features but also with similar crystallochemical characteristics.

https://iopscience.iop.org/article/10.1088/0022-3727/36/13/202/pdf

The preparation of magnetic nanoparticles for applications in biomedicine

http://files.janapv.webnode.cz/200000097-8a03f8afdf/ex_bias_nano.pdf

Exchange bias in nanostructures

Oxygen evolution reaction (OER) electrolysis, as an important reaction involved in water splitting and rechargeable metal-air batteries, has attracted increasing attention for clean energy generation and efficient energy storage. Nickel/iron (NiFe)-based compounds have been known as active OER catalysts since the last century, and renewed interest has been witnessed in recent years on developing advanced NiFe-based materials for better activity and stability. In this review, we present the early discovery and recent progress on NiFe-based OER electrocatalysts in terms of chemical properties, synthetic methodologies and catalytic performances. The advantages and disadvantages of each class of NiFe-based compounds are summarized, including NiFe alloys, electrodeposited films and layered double hydroxide nanoplates. Some mechanistic studies of the active phase of NiFe-based compounds are introduced and discussed to give insight into the nature of active catalytic sites, which could facilitate further improving NiFe based OER electrocatalysts. Finally, some applications of NiFe-based compounds for OER are described, including the development of an electrolyzer operating with a single AAA battery with voltage below 1.5 V and high performance rechargeable Zn-air batteries. 
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A mini review of NiFe-based materials as highly active oxygen evolution reaction electrocatalysts

Some of the most relevant finite-size and surface effects in the magnetic and transport properties of magnetic fine particles and granular solids are reviewed. The stability of the particle magnetization, superparamagnetic regime and the magnetic relaxation are discussed. New phenomena appearing due to interparticle interactions, such as the collective state and non-equilibrium dynamics, are presented. Surface anisotropy and disorder, spin-wave excitations, as well as the enhancements of the coercive field and particle magnetization are also reviewed. The competition of surface and finite-size effects to settle the magnetic behaviour is addressed. Finally, two of the most relevant phenomena in the transport properties of granular solids are summarized namely, giant magnetoresistance in granular heterogeneous alloys and Coulomb gap in insulating granular solids.

https://iopscience.iop.org/article/10.1088/0022-3727/35/6/201/pdf

Finite-size effects in fine particles: magnetic and transport properties

Ordered magnetic nanostructures: fabrication and properties

Nickel ferrite nanoparticles exhibit anomalous magnetic properties at low temperatures: low magnetization with a large differential susceptibility at high fields, hysteresis loops which are open up to 160 kOe, time-dependent magnetization in 70 kOe applied field, and shifted hysteresis loops after field cooling. We propose a model of the magnetization within these particles consisting of ferrimagnetically aligned core spins and a spin-glass-like surface layer. We find that qualitative features of this model are reproduced by a numerical calculation of the spin distribution. Implications of this model for possible macroscopic quantum tunneling in these materials are discussed.

Surface Spin Disorder in NiFe2O4 Nanoparticles.

Anomalous magnetic properties of organic coated NiFe2O4 nanoparticles have been reported previously (Berkowitz et al.).5 These properties included low magnetization with a large differential susceptibility at high fields and shifted hysteresis loops after field cooling, while Mossbauer spectra indicated that all of the material was magnetically ordered. In the present study, we find that the lack of saturation in high fields is accompanied by irreversibility (i.e., hysteresis loops are open) up to 160 kOe. In addition, the particles exhibit time dependent magnetization in 70 kOe applied field. The high field irreversibility and the loop shift both vanish above 50 K. We propose a model of the magnetization within these particles consisting of ferrimagnetically aligned core spins and a spin- glass-like surface layer. We find that qualitative features of this model are reproduced by a numerical calculation of the spin distribution. The implications of this model for possible macroscopic quantum tunneling in these materials are discussed.

Surface spin disorder in ferrite nanoparticles (invited)

Anomalous properties of magnetic nanoparticles

Surface Spin Disorder in Ferrite Nanoparticles

The phenomenon of giant intrinsic magnetic hardness in SmCo5−x Ni x and SmCo5−y Cu y is investigated in applied fields up to 23.5 T. At 4.2 K, the average propagation field (approximate coercive field)H p is ≃13.0 T, 22.0 T and 18.2 T for x=3, 3.6 and 4.2 respectively, and H p is ≃12.0 and ≃23.0 T for y=2.5 and 3.6 respectively. At 77 K, values of H p ≃5.0 and ≃5.5 T for y=2.5. Some values of H p at 4.2 K are the largest observed to date for any material. The results are consistent with models for thermally activated domain wall motion. For several materials the irreversible portion of the magnetization is not saturated at 23 T and 4.2 K. In these cases the maximum magnetization is less than that observed at 77 K.

S. Foner

Papers

Surface Spin Disorder in NiFe2O4 Nanoparticles.

Surface spin disorder in ferrite nanoparticles (invited)

Anomalous properties of magnetic nanoparticles

Surface Spin Disorder in Ferrite Nanoparticles

High field measurements of giant intrinsic magnetic hardness in SmCo5−xNix and SmCo5−yCuy