Home > Article > Advanced Magnetic Materials

Advanced Magnetic Materials

Advanced Magnetic MaterialsAll chapters are open access distributed under the creative Commons Attribution 30to downloposes, as long as the author and publisher are properimum dissemination and a wider impact of our publications Afteras been published by In Techhave the righwhole or partwhich they are the author, arse of thework

Anyal purposes, as long as the author and publisher are properlymum dissemination and a wider impact of our publicatioexpressed in the chapters are these of the individual contributonot necessarily those of the editors or publisher No responsibilitycontained in the published chapters the publioT anythe booechnical editor teodoraAdditional haorders@dvanceddited bySBN978953-51-063

identification of the magnetic properties of the material in an electromagnetidevices consist of a large number of magnetic doma: es,Chapter 8 The last chapter tackles the problemgnetichich interact and evTherefore,magnetic hysteresis isthe most difficult tasks in magnetism

This chapterprovides a detailed desodel for modeling of magnetizationagnetbased on a stochastic preisachbolic analytical approximation of the Everett integral The theng of coercive force, remanent magnetization, hysteretic losses, Barkhauseneddy current losses, exchange bias and other essential properties of them of advanced materials, It will also bring betterunderstanding of challenging technologies which become a part of our life, whe use computers, cell phones and other modern devicesDr Leszek malinskiociate Professor of Physics and Materials Science,Department of Physics and the Advanced Materials Research Institute,University of New Orleans, New Orleans, Louisiana,

Rapidly solidified MagneticNanowires and submicron wiresNational Institute of Research and Development for Technical Physics lasiRomaniaMagnetically soft amorphous glass-coated microwires are suitable for numpplications Their typical dimensions- metallic nucleus diameter of 1 to 50 um and glating thickness of 1 to 30 um -make them promising candidates for high frequencyplications, especially given their sensitive giant magneto-impedance(GMi) response inthe MHz and GHz ranges (Torrejon et al, 2009) The magnetic properties of amorphousmicrowires are determined by composition, which gives the sign and magnitude of theirthickness, and their ratiohichfor the level of internal stresluced during preparation The magneto-mechanical coupling between internal stressesmagnetostriction is mainly responsible for the distribution of anisotropy axes andomain structure formation Microwires generally display a core-shell domain structuretheir metallic nucleus, with orthogonal easy axes, e

g axial in the core and circumferential ordial in the shell, as schematically shown in Fig 1OS: Outer Shell入>0Fig 1 Typicaldomain structures in amorphous glass-coated microwires withpositive >0)and nearly zernetostriction(%=O), respectively

Advanced Magnetic MateriaBarkhausen effect (LBE), that is a single stepthebjected to a small axial magnetictakes place through thpropagation of a pre-existent 180 domain wall from one microwire end to the other, asry, magnetic domain wall logic devices, domain wall diodes and oscillators, andbased on fielddomain wall motion(Allwood et al005: Finocchio et al, 2010: Lee et al 2007: Parkin et al 2008) These applicatibe accurately controlled and tailoreddomain wall velocities, since the device speed depends on domain wall velocity At presenthich reqprepared by expensive lithographic methods(Moriya et al, 2010)Recently, the larall velocity reported in amorphous glass-coatedet al, 200 7) prospects for the use of these much cheaper rapidly solidifiedbject to a significant reduction in their diameterus nanowires aress coating prepared in a single stage process, the glass-Orated melt spinning, at sample lengths of the order of 10- m(Chiriac Ovari, 1996) Inf such ultrathinwires and to drastically reduce the typical transverse dimensions of microwires(1 to 50 umfor the metallic nucleiameter), the apparatus used for the preparation of the rapidllidified nanowires has been significantly modified These efforts have led to the successfulharacterization of rapidly solidified submicron wires withmetallicnucleus diameter of 800 nm, reported less than 2 years ago( Chiriac et al

, 2010) Figure 2(ashows the sEM images of a submicmorphous wire with the nucleus diameter of 800nm, whilst Fig 2(b)illustrates the optical microscopy image of the submicron amorph47 and 18 um, respectively These results have opened up the opportunity to developnanosized rapidly solidified amorphous magnetic materials for applications based on thedomain wall motioThis first suhas been shortly followed by theon and characterization ofass-coated submicronwith metallic(Chiriac et al, 201la), in which domain wall velocityshpromising results(Ovari et aL, 201The well-known methods employed in the experimstudies have been extensivelpin order to alomplex measurements on such thined toCorodeanu et al, 2011a)been able to produce rapidltechnique, The diameters of thewere ranging from 90 to 180 nm( Chiriac et al, 2011b) These new materials are

apidly Solidified Magnetic Nanowires and Submicron wiresmorphous wire in comparisontypical amorphous microwires with the nucleus diameters of 47 and 1

8 um, respectivelypplications in both domain wall logic type devices and in novel, miniature sensors Theaccurate control of the domain wall motion could be performed without irreversibNevertheless, there are several issues to be addressed before ththeir full practical potential:methods to prepare the moils required to inject and trap domain walls, theclarification of the role of glg and whether or not it should be kept, removed or just

Advanced Magnetic Materiamoved- and in which stages of the device development,Figure 3 shows two SEM micrographs of a glass-coated Fen, sSizsB1with the metallic nucleus diameter of 90Hm, takeng 3 SEM micrographs at two different magnifications of a rapidly solidified amorphousanowire with positive magnetostriction having the metallic nucleus ddnew method for measuring the domain wall velocity in aultrathin ferromagneticire with the diameter down to 100oed in order to measuret al, 2011b) The method has been developed in order toease the sensitivity in studying the domain wall propagation in bistable magnetic wires inwide range of field amplitudes, with much larger values of the applied field as compared toed when studying the wall propagation in typicrphous microwires Thenewly developed method isally important now, when large effort is devoted to thedrapidly soliemagnetic domain structure, which makes the b

istable behavior possible a ges in thend in thewitching field, at submicron level and at nanoscale2 Experimental techniques for the characterization of rapidly solidifiedwires

Domain walnucleus diametersnanometers and hundredscharacterization techtypicalButta et al 2009:order to measure their basic magnetic properties, eg to determine their magnetic hysteresis

Solidified Magnetic Nanowires and Submicron wiresloops, is not viable due to the low sensitivity and signal-to-noise ratio (SNR) Therefore, inmagnetic properties of a single ultrathin magnetic wire, a reliableeasuring system has been developed (Corodeanu et al 2011a) The new procedure hasbeen employed teusing a digital integration technicental set-up has beendeveloped in order tothetivity and to extractnoisy signal a reliablw frequencis loop for a single submicron wire ormagnetizingthe system of pick-up coils,reamplifier, a functiontion board a schematic of the system is shown in Fig 4

MultimeterHSAData AcquisitiComputerSR560PCI-61 15Fig 4 Schematic of the experimental system employed for the magnetic characterization ofThe magnetizing solenoid is pthrough a high power bipolar amplifier HSA 4014, being capable of generating magneticd any induced voltage in the absence of the sample, Each pick-up coil isouter diameter of 1 8 mm and an inner diameter of 1 mm, A 1 Q resistor(R) is used tofield The voltage induced in th>amplifier in order to obtain a measurable value of the induced voltage and a high SNRhe voltage drop on the resistor R and the amplified induced voltage from the pickystem are digitized using a National Instruments PCI-6115 four channelsdata acquisition board The acquisition of the signals was done using a sampling frequenbetween 800 kHz and 10 MHz (with 5,000 to 62,500 points/ loop at 160 Hz) TheTwo methods have been employed tothe hysteresis loops For the firstnumber of acquired signals, while for thene only two recordings of the signal were required (with and without the sample)followed by digital processing to trace the hysteresis loop

NTECHfree online editions of Intewww


ontentsNanowires and submicron wires 1Chaoperties of Magnetite for SpiGareth s Parkinson Ulnke Dieboldke Tang and Leszek Malinski4 Biomedical Applications of Multiferroic Nanoparticles 89Chagh Frequency DC-DC Power Converters 119ddad

cC33hapter 7 Magnetic Material characterizationcal Approximation 20

PrefaceRecent progress in infond microelectronics requires advanced technologies and new magnetic materials topublished contributions from the renowned scientists in the field of magnetism Thebook is addressed to a diroup of readers which include students, engineers andresearchersthe fields of phchemistry, bioengineering,materials science, who wish to enrich their knowledge about advancedDepending on the dise represented by the readers thebook or select chapters of particular interest In order to help with the choice ofpropriate chapters below I summarize their contentChapter 1 The first chapter reports on fabrication method of amorphous magnetnanowires with the glass coating using rapid solidification of the melt

The originaent methods and magnetic properties of the nanowires with the diametersrangingto 1n particular, the articlets the effectof fabn conditions and post-fabrication treatment on mobility and velocity ofdomain walls in the nanowires, which can be used in futurekoriesmagnetic domain wall logic devices, domain wall diodes and oscillators, and otheChapter 2 Futurfrequency range This chapter treats about new developments in technology andum hexagonal ferrite filmstremely high anisotromicrowave range The author demonstrates original results regarding prototype notchfilters and phase shifters operating at millimeter range wavelengths which employ theging field of science which takesof magnetic moments to build nonvolatile random aces anddevices In order to compete and eventually replace semiconductor-basedthe spintronic devices must use materials with nearly 100% spin

Prefacepolarization The magnetite is one of the best candidates for the spintronicpplications However, its perexisting devices is drastically reducedthe atomic structure at the surface which differs from that of the bulk This chapterpresents studies of surface reconstruction of the magnetite and describes methods forincreasing spin efficiency in spintronic devices by preserving the FexO4 structure of theChapter 4 Multiferroic composites consisting of ferromagnetic and ferroelectricmaterialsof converting magnetic field into electric field Thiprocess involves stresses at the interface between these materials and takes advantageelectricity of the ferroelectric and thection of the ferromagnetphase This chapter describes original methodsnanoparticles and indicates entirely new biomedical applicationssuchnoparticles Using external alternating magnetic fields it is possible to produce locallectric fields near multiferroic nanoparticles whichtrol opening and closing ofvoltage-gated ion channels in mammalian cells Ion channels areneration and propagation of action potentiaerves and their malfunction canead to multiple diseases such as cystic fibrosis, diabetes, cardiac arrhythmianeurological disorders or hypertension

The proposed mechanism has also potentiahapter 5 One of challenges in the designble electronic devices is theoptimization of on-chip inductors for the power conversion This optimultiple factors, such as size, a choice of fabrications method,ange of operation, energy losses and cost of the device This chapter pdiscussion about theory, design, fabrication methods and measurements ofparameters characterizing electroplated micro-inductors for DC-DC conversionoperating with the switching frequency up to 100 MHzChapter 6 The focus of this chapter is on the relation betweendisorder in the fe-Althe cordifferent magnetic and structural ordexist in this system including a spin-glassrder Detailed experimental studies based on magnetometry, the Mossbauer effectell as theoretical models of this system show that thetomic disorder, which can be controlled by a mechanical treatment or an annealing,significant increase in the lattice parameters and the magnetization comparedto those in the ordered structures The contribution of disorder to the magnetism ofthese alloys depends on the Fe content of the alloy and is the largest close to the equiatomic feal alloy but in fezs ahs alloy it is similar to the one given by the volu7 Direct characterizationhe magneticThis chapter proposes the state-oflogy to extract matericharacteristics from the measurements of electromagnetic devices This original