In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Hexagonal ferrites: A review of the synthesis, properties and applications of hexaferrite ceramics

Multiferroic magnetoelectric composite systems such as ferromagnetic-ferroelectric heterostructures have recently attracted an ever-increasing interest and provoked a great number of research activities, driven by profound physics from coupling between ferroelectric and magnetic orders, as well as potential applications in novel multifunctional devices, such as sensors, transducers, memories, and spintronics. In this Review, we try to summarize what remarkable progress in multiferroic magnetoelectric composite systems has been achieved in most recent few years, with emphasis on thin films; and to describe unsolved issues and new device applications which can be controlled both electrically and magnetically.

Recent Progress in Multiferroic Magnetoelectric Composites: from Bulk to Thin Films

https://www.andrew.cmu.edu/user/dl0p/laughlin/pdf/PMS.pdf

Amorphous and nanocrystalline materials for applications as soft magnets

This tutorial review summarizes the recent advances in the chemical synthesis and potential applications of monodisperse magnetic nanoparticles. After a brief introduction to nanomagnetism, the review focuses on recent developments in solution phase syntheses of monodisperse MFe2O4, Co, Fe, CoFe, FePt and SmCo5 nanoparticles. The review further outlines the surface, structural, and magnetic properties of these nanoparticles for biomedicine and magnetic energy storage applications.

Magnetic nanoparticles: synthesis, functionalization, and applications in bioimaging and magnetic energy storage

The development of Fe73.5Si13.5B9Nb3Cu1 (FINEMET) by Yoshizawa et al. and Fe88Zr7B4Cu1 (NANOPERM) by Inoue et al. have shown that nanocrystalline microstructures can play an important role in the production of materials with outstanding soft magnetic properties. The FINEMET and NANOPERM materials rely on nanocrystalline α-Fe3Si and α-Fe, respectively, for their soft magnetic properties. The magnetic properties of a new class of nanocrystalline magnets are described herein. These alloys with a composition of (Fe,Co)–M–B–Cu (where M=Zr and Hf) are based on the α- and α′-FeCo phases, have been named HITPERM magnets, and offer large magnetic inductions to elevated temperatures. This report focuses on thermomagnetic properties, alternating current (ac) magnetic response, and unambiguous evidence of α′-FeCo as the nanocrystalline ferromagnetic phase, as supported by synchrotron x-ray diffraction. Synchrotron data have distinguished between the HITPERM alloy, with nanocrystallites having a B2 structure from the ...

Structure and magnetic properties of (Fe0.5Co0.5)88Zr7B4Cu1 nanocrystalline alloys

Multiferroic heterostructures of Fe 3 O 4/ PZT (lead zirconium titanate), Fe 3 O 4 / PMN-PT (lead magnesium niobate-lead titanate) and Fe 3 O 4 /PZN-PT (lead zinc niobate-lead titanate) are prepared by spin-spray depositing Fe 3 O 4 ferrite film on ferroelectric PZT, PM N-PT and PZN-PT substrates at a low temperature of 90 °C. Strong magnetoelectric coupling (ME) and giant microwave tunability are demonstrated by a electrostatic field induced magnetic anisotropic field change in these heterostructures. A high electrostatically tunable ferromagnetic resonance (FMR) field shift up to 6000e, corresponding to a large microwave ME coefficient of670e cm kV ―1 , is observed in Fe 3 O 4 /PMN-PT heterostructures. A record-high electrostatically tunable FMR field range of 860 Oe with a linewidth of 330―380 Oe is demonstrated in Fe 3 O 4 /PZN-FT heterostructure, corresponding to a ME coefficient of 08 Oe cm kV ―1 . Static ME interaction is also investigated and a maximum electric field induced squareness ratio change of 40% is observed in Fe 3 O 4 /PZN-PT In addition, a new concept that the external magnetic orientation and the electric field cooperate to determine microwave magnetic tunability is brought forth to significantly enhance the microwave tunable range up to 10000e. These low temperature synthesized multiferroic heterostructures exhibiting giant electrostatically induced tunable magnetic resonance field at microwave frequencies provide great opportunities for electrostatically tunable microwave multiferroic devices.

Giant Electric Field Tuning of Magnetic Properties in Multiferroic Ferrite/Ferroelectric Heterostructures

Ferromagnetic air-stable SmCo nanoparticles have been produced directly using a one-step chemical synthesis method. X-ray diffraction studies confirmed the formation of hexagonal SmCo5 as a dominant phase. High resolution transmission electron microscopy confirms the presence of uniform, anisotropic bladelike nanoparticles approximately 10nm in width and 100nm in length. Values of the intrinsic coercivity and the magnetization in the as-synthesized particles are 6.1kOe and 40emu∕g at room temperature and 8.5kOe and 44emu∕g at 10K, respectively. This direct synthesis process is environmentally friendly and is readily scalable to large volume synthesis to meet the needs for the myriad of advanced permanent magnet applications.

https://repository.library.northeastern.edu/files/neu:330511/fulltext.pdf

Direct chemical synthesis of high coercivity air-stable SmCo nanoblades

The sensitive response of the dielectric permittivity under the application of magnetic fields in Mn0.60Zn0.40Fe2.12O4+δ polycrystalline ferrite is presented. A magnetic field of 3.5 kOe induced a giant magnetodielectric {MD=[e′(H)−e′(0)]/e′(0)} response, of 1800% at f=7 MHz, at room temperature. The ferrite exhibits a large magnetic field-induced frequency response of 180 Hz/Oe. We suggest that this effect arises primarily from a spin-dependent space charge polarization mechanism in response to the application of dc magnetic fields.

Giant magnetodielectric effect and magnetic field tunable dielectric resonance in spinel MnZn ferrite

A miniature, quasi one dimensional, magnetic field sensor based on magnetoelectric coupling is presented. The magnetoelectric sensor makes use of the d31 coupling mode between a piezoelectric lead zirconate titanate tube and FeNi magnetostrictive wire. The sensors demonstrate high sensitivity, high signal-to-noise ratio, and low noise floor at zero DC magnetic bias field and at low frequency resulting in smaller, lower power consumption, and volumetric efficiency. Experiments indicate a zero bias field sensitivity of 16.5 mV/Oe at 100 Hz stemming from a magnetoelectric coefficient of 1.65 V/cm-Oe. The results are quantitatively described by a theoretical model of laminate composites.

V. G. Harris

Papers

Structure and magnetic properties of (Fe0.5Co0.5)88Zr7B4Cu1 nanocrystalline alloys

Giant Electric Field Tuning of Magnetic Properties in Multiferroic Ferrite/Ferroelectric Heterostructures

Direct chemical synthesis of high coercivity air-stable SmCo nanoblades

Giant magnetodielectric effect and magnetic field tunable dielectric resonance in spinel MnZn ferrite

Quasi-one-dimensional miniature multiferroic magnetic field sensor with high sensitivity at zero bias field