Multiferroic and Magnetoelectric Hexagonal Ferrites

Abstract

The hexagonal ferrites, also known as hexaferrites, have become massively important materials commercially and technologically, accounting for the bulk of the total magnetic materials manufactured globally, and they have a multitude of uses and applications. As well as their use as permanent magnets, common applications are as magnetic recording and data storage materials, and as components in electrical devices, particularly those operating at microwave/GHz frequencies for mobile and wireless communications, electromagnetic wave absorbers for electromagnetic compatibility (EMC), radar absorbing materials (RAM) and stealth technologies. One of the most exciting recent developments has been the discovery of single phase magnetoelectric/multiferroic hexaferrites, IntroductionThe hexagonal ferrites are magnetic iron(III)-based oxides with a hexagonal crystal structure (Fig. 7.1), also known as hexaferrites. They have become massively important materials commercially and technologically, and hexaferrites are used in a multitude of applications, for example permanent magnets, electrical motors and transformers, actuators and sensors, information storage, mobile communications, transport, security, defence and aerospace [1]. M-type hexaferrites account for over 90 % of the total permanent magnetic materials

Uniaxial ferroelectric quantum criticality in multiferroic hexaferrites BaFe12O19 and SrFe12O19

“…300,000 tons of hexagonal BaFe 12 O 19 are produced every year, which corresponds to 50 grams for every person on Earth12. Primary uses are magnetic credit cards, bar codes, and small motors, as well as low-loss cheap microwave devices.…”

Broadband transverse susceptibility in multiferroic Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22

“…In addition, under an applied magnetic field different magnetization curves have been obtained at different measuring temperatures, some of them with bends caused by the undergoing spin transitions that take place in BSZFO. The different magnetic structures change from planar helix to collinear ferrimagnetic ordering, with several intermediate commensurate magnetic spin phases with mixed conical structure, called I, II and III (the spin orientations in this phases can be seen in [4,8,19]). For each composition, some of the above, as well as alternate longitudinal conical (ALC) and transverse conical (TC) can take place at different values of temperature and applied magnetic field leading to a complex magnetic phase diagram [4,8,35,36].…”

“…Magnetoelectric multiferroics have attracted significant interest in recent research activities because they can present unusual physical phenomena like remarkable magnetoelectric effects with potential applications in ultra-dense magnetic storage devices, as low power spintronic devices, or effective medical drug delivery [1][2][3][4]. Among the compounds with this characteristic, ferroxplana type hexaferrites with Z and Y phases are very promising materials, due to the giant magnetoelectric coupling between magnetism and ferroelectricity caused by the spin transitions from longitudinal to transverse helimagnetic phases and the low magnetic fields to switch the electric polarization [5][6][7].…”

Ferroelectric Relaxor Quantum Crystals

“…An obvious extension is to magnetoelectric QCPs, and some work on the BaFe 12 O 19 hexaferrite family has already been reported [1][2][3][4][5][6][7][8][9][10][54][55][56][57][58][59][60][61]. This material is very popular, because it is the usual material in magnetic-stripe credit cards, with >$1 billion/year in sales as a magnetic compound [60,61].…”

“…This material is very popular, because it is the usual material in magnetic-stripe credit cards, with >$1 billion/year in sales as a magnetic compound [60,61].…”