Barium ferrite

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Contents

Barium ferrite
Barium ferrite crystal structure.png
Barium ferrite crystal structure
Identifiers
3D model (JSmol)
ECHA InfoCard 100.031.782 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/Ba.12Fe.19O
    Key: AJCDFVKYMIUXCR-UHFFFAOYSA-N
  • O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Ba]
Properties
BaFe12O19
Molar mass 1111.448 g·mol−1
Appearanceblack solid
Density 5.28 g/cm3
Melting point 1,316 °C (2,401 °F; 1,589 K)
insoluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Barium ferrite , abbreviated BaFe, BaM, is the chemical compound with the formula BaFe
12O
19 (BaO : 6 Fe
2O
3). [1] This and related ferrite materials are components in magnetic stripe cards and loudspeaker magnets.

BaFe is described as Ba2+
Fe3+
12O2−
19. The Fe3+
 centers are ferrimagnetically coupled, and one unit cell of BaM has a net magnetic moment of 40μB. [2] This area of technology is usually considered to be an application of the related fields of materials science and solid state chemistry.

Barium ferrite is a highly magnetic material, has a high packing density,[ clarification needed ] and is a metal oxide. Studies of this material date at least as far back as 1931, [3] and it has found applications in magnetic card strips, speakers, and magnetic tapes. [1] One area in particular it has found success in is long-term data storage; the material is magnetic, resistant to temperature change, corrosion and oxidization. [4]

Chemical structure

The Fe3+
 centers, with a high-spin d 5 configuration, are ferrimagnetically coupled. [2] [5] This area of technology is usually considered to be an application of the related fields of materials science and solid state chemistry.

A related family of industrially useful "hexagonal ferrites" are known, also containing barium. [1] In contrast to the usual spinel structure, these materials feature hexagonal close-packed framework of oxides. Furthermore, some of the oxygen centers are replaced by Ba2+
 ions. Formulas for these species include BaFe
12O
19, BaFe
15O
23, and BaFe
18O
27. [6]

A one-step hydrothermal process can be used to form crystals of barium ferrite, by mixing barium chloride, ferrous chloride, potassium nitrate, and sodium hydroxide with a hydroxide to chloride concentration ratio of 2:1. Nano-particles are prepared from ferric nitrate, barium chloride, sodium citrate, and sodium hydroxide. [7] The typical preparation, however, is by calcining barium carbonate with iron(III) oxide: [8]

BaCO
3 + 6  Fe
2O
3 BaFe
12O
19 + CO
2

Properties

Barium ferrite has been considered for long term data storage. The material has proven to be resistant to a number of different environmental stresses, including humidity and corrosion. Because ferrites are already oxidized it can not be oxidized any further. This is one reason ferrites are so resistant to corrosion. [9] Barium ferrite also proved to be resistant to thermal demagnetization, another issue common with long-term storage. [4] The Curie temperature is typically around 450 °C (723K).

When barium ferrite magnets increase in temperature, their high intrinsic coercivity improves, this is what makes it more resistant to thermal demagnetization. Ferrite magnets are the only type of magnets that become substantially more resistant to demagnetization as temperature increases. This characteristic of barium ferrite makes it a popular choice in motor and generator designs and also in loudspeaker applications. Ferrite magnets can be used in temperatures up to 300 °C, which makes it a perfect to be used in the applications mentioned above. Ferrite magnets are extremely good insulators and don't allow any electrical current to flow through them and they are brittle which shows their ceramic characteristics. Ferrite magnets also have good machining properties, which allows for the material to be cut in many shapes and sizes. [10]

Chemical properties

Barium ferrites are robust ceramics that are generally stable to moisture and corrosion-resistant. [9] Ba‑Fe ferrite is an oxide, so it does not break down due to oxidation as much as a metal alloy might; giving Ba‑Fe a much greater life expectancy. [4]

Mechanical properties

Metal particles (MP) have been used to store data on tapes and magnetic strips but they have reached their limit for high capacity data storage. In order to increase their capacity by (25×) on data tape the MP had to increase the tape length by (45%) and track density by over (500%) which made it necessary to reduce the size of the individual particles. As the particles were reduced in size, the passivizing coating needed to prevent the oxidation and deterioration of the MP had to become thicker. This presented a problem for as the passivation coating got thicker it became harder to achieve an acceptable signal to noise ratio.

Barium ferrite completely out classes MP, mostly because Ba‑Fe is already in its oxidized state and so is not restricted in its size by a protective coating. Also due to its hexagonal pattern it is easier to organize compared to the unorganized rod like MP. Another factor is the difference in the size of the particles, in MP the size ranges from 40 to 100 nm while the Ba‑Fe is only 20 nm. So the smallest MP particle is still double the size of the BaFe particles. [11]

Applications

Barium Ferrite is used in tape drives and floppy disks. Dds tape drive 01.jpg
Barium Ferrite is used in tape drives and floppy disks.

Barium ferrite is used in applications such as recording media, permanent magnets, and magnetic stripe cards (credit cards, hotel keys, ID cards). Due to the stability of the material, it is able to be greatly reduced in size, making the packing density much greater. Earlier media devices utilized doped acicular oxide materials to yield the coercivity values necessary to record. In recent decades, barium ferrite has replaced acicular oxides; without any dopants, the acicular oxides produce very low coercivity values, making the material very magnetically soft, while barium ferrite's higher coercivity levels make the material magnetically hard and thus a superior choice for recording material applications.

Magnetic Stripes

ID cards using barium ferrite are made with a magnetic fingerprint that identifies them, allowing readers to self-calibrate. [12]

Speaker magnets

Barium ferrite is a common material for speaker magnets. The materials can be formed into almost any shape and size using a process called sintering, whereby powdered barium ferrite is pressed into a mold, and then heated until it fuses together. The barium ferrite turns into a solid block while still retaining its magnetic properties. The magnets have an excellent resistance to demagnetization, allowing them to still be useful in speaker units over a long period of time. [13]

Tape Data Storage Media

Barium ferrite is used for enterprise level [14] and commodity linear tape-open (LTO) tape storage media. Because of its high density, barium ferrite has led to data capacity improvements in both enterprise and LTO tapes over prior metal particle (MP) media technology. [15]

Developments in the field have also resulted in the reduction of the size of BaFe particles to about 20 nm. This contrasts with MP technology, which has problems shrinking the particles past 100 nm. [4] Barium ferrite has better packing properties than most other metal particles because of the distinctive shape of the particles. [4] This leads to better control over magnetic orientation and improved signal-to-noise characteristics. [14]

Natural occurrence

The compound occurs in nature, although is exceedingly rare. It is called barioferrite and is related to pyrometamorphism. [16] [17]

Related Research Articles

<span class="mw-page-title-main">Ferromagnetism</span> Mechanism by which materials form into and are attracted to magnets

Ferromagnetism is a property of certain materials that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagnetic materials are familiar metals that are noticeably attracted to a magnet, a consequence of their substantial magnetic permeability. Magnetic permeability describes the induced magnetization of a material due to the presence of an external magnetic field. This temporarily induced magnetization, for example, inside a steel plate, accounts for its attraction to the permanent magnet. Whether or not that steel plate acquires a permanent magnetization itself depends not only on the strength of the applied field but on the so-called coercivity of the ferromagnetic material, which can vary greatly.

<span class="mw-page-title-main">Tape drive</span> Data storage device

A tape drive is a data storage device that reads and writes data on a magnetic tape. Magnetic-tape data storage is typically used for offline, archival data storage. Tape media generally has a favorable unit cost and a long archival stability.

<span class="mw-page-title-main">Magnet</span> Object that has a magnetic field

A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets.

Ferrite may refer to:

<span class="mw-page-title-main">Ferrimagnetism</span> Type of magnetic phenomenon

A ferrimagnetic material is a material that has populations of atoms with opposing magnetic moments, as in antiferromagnetism, but these moments are unequal in magnitude so a spontaneous magnetization remains. This can for example occur when the populations consist of different atoms or ions (such as Fe2+ and Fe3+).

Remanence or remanent magnetization or residual magnetism is the magnetization left behind in a ferromagnetic material after an external magnetic field is removed. Colloquially, when a magnet is "magnetized", it has remanence. The remanence of magnetic materials provides the magnetic memory in magnetic storage devices, and is used as a source of information on the past Earth's magnetic field in paleomagnetism. The word remanence is from remanent + -ence, meaning "that which remains".

<span class="mw-page-title-main">Coercivity</span> Resistance of a ferromagnetic material to demagnetization by an external magnetic field

Coercivity, also called the magnetic coercivity, coercive field or coercive force, is a measure of the ability of a ferromagnetic material to withstand an external magnetic field without becoming demagnetized. Coercivity is usually measured in oersted or ampere/meter units and is denoted HC.

<span class="mw-page-title-main">Alnico</span> Family of iron alloys

Alnico is a family of iron alloys which in addition to iron are composed primarily of aluminium (Al), nickel (Ni), and cobalt (Co), hence the acronym al-ni-co. They also include copper, and sometimes titanium. Alnico alloys are ferromagnetic, and are used to make permanent magnets. Before the development of rare-earth magnets in the 1970s, they were the strongest type of permanent magnet. Other trade names for alloys in this family are: Alni, Alcomax, Hycomax, Columax, and Ticonal.

A samarium–cobalt (SmCo) magnet, a type of rare-earth magnet, is a strong permanent magnet made of two basic elements: samarium and cobalt.

<span class="mw-page-title-main">Rare-earth magnet</span> Strong permanent magnet made from alloys of rare-earth elements

A rare-earth magnet is a strong permanent magnet made from alloys of rare-earth elements. Developed in the 1970s and 1980s, rare-earth magnets are the strongest type of permanent magnets made, producing significantly stronger magnetic fields than other types such as ferrite or alnico magnets. The magnetic field typically produced by rare-earth magnets can exceed 1.2 teslas, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla.

<span class="mw-page-title-main">Ferrite (magnet)</span> Ferrimagnetic ceramic material composed of rust and a metallic element

A ferrite is a ceramic material made by mixing and firing iron(III) oxide with one or more additional metallic elements, such as strontium, barium, manganese, nickel, and zinc. They are ferrimagnetic, meaning they are attracted by magnetic fields and can be magnetized to become permanent magnets. Unlike other ferromagnetic materials, most ferrites are not electrically conductive, making them useful in applications like magnetic cores for transformers to suppress eddy currents. Ferrites can be divided into two families based on their resistance to being demagnetized.

<span class="mw-page-title-main">Chromium(IV) oxide</span> Chemical compound

Chromium dioxide or chromium(IV) oxide is an inorganic compound with the formula CrO2. It is a black synthetic magnetic solid. It once was widely used in magnetic tape emulsion. With the increasing popularity of CDs and DVDs, the use of chromium(IV) oxide has declined. However, it is still used in data tape applications for enterprise-class storage systems. It is still considered by many oxide and tape manufacturers to have been one of the best magnetic recording particulates ever invented.

In electronics, a ferrite core is a type of magnetic core made of ferrite on which the windings of electric transformers and other wound components such as inductors are formed. It is used for its properties of high magnetic permeability coupled with low electrical conductivity. Moreover, because of their comparatively low losses at high frequencies, they are extensively used in the cores of RF transformers and inductors in applications such as switched-mode power supplies, and ferrite loopstick antennas for AM radio receivers.

<span class="mw-page-title-main">Iron oxide nanoparticle</span>

Iron oxide nanoparticles are iron oxide particles with diameters between about 1 and 100 nanometers. The two main forms are composed of magnetite and its oxidized form maghemite. They have attracted extensive interest due to their superparamagnetic properties and their potential applications in many fields including molecular imaging.

Zinc ferrites are a series of synthetic inorganic compounds of zinc and iron (ferrite) with the general formula of ZnxFe3−xO4. Zinc ferrite compounds can be prepared by aging solutions of Zn(NO3)2, Fe(NO3)3, and triethanolamine in the presence and in the absence of hydrazine, or reacting iron oxides and zinc oxide at high temperature. Spinel (Zn, Fe) Fe2O4 appears as a tan-colored solid that is insoluble in water, acids, or diluted alkali. Because of their high opacity, zinc ferrites can be used as pigments, especially in applications requiring heat stability. For example, zinc ferrite prepared from yellow iron oxide can be used as a substitute for applications in temperatures above 350 °F (177 °C). When added to high corrosion-resistant coatings, the corrosion protection increases with an increase in the concentration of zinc ferrite.

In magnetism, single domain refers to the state of a ferromagnet in which the magnetization does not vary across the magnet. A magnetic particle that stays in a single domain state for all magnetic fields is called a single domain particle. Such particles are very small. They are also very important in a lot of applications because they have a high coercivity. They are the main source of hardness in hard magnets, the carriers of magnetic storage in tape drives, and the best recorders of the ancient Earth's magnetic field.

<span class="mw-page-title-main">Permanent magnet motor</span> Type of electric motor

A permanent magnet motor is a type of electric motor that uses permanent magnets for the field excitation and a wound armature. The permanent magnets can either be stationary or rotating; interior or exterior to the armature for a radial flux machine or layered with the armature for an axial flux topology. The schematic shows a permanent magnet motor with stationary magnets outside of a brushed armature.

Magnadur is a sintered barium ferrite, specifically BaFe12O19 in an anisotropic form. It is used for making permanent magnets. The material was invented by Mullard and was used initially particularly for focussing rings on cathode ray tubes. Magnadur magnets retain their magnetism well, and are often used in education. Magnadur can also be used in DC motors.

<span class="mw-page-title-main">Compact Cassette tape types and formulations</span>

Audio compact cassettes use magnetic tape of three major types which differ in fundamental magnetic properties, the level of bias applied during recording, and the optimal time constant of replay equalization. Specifications of each type were set in 1979 by the International Electrotechnical Commission (IEC): Type I, Type II, Type III, and Type IV. 'Type 0' was a non-standard designation for early compact cassettes that did not conform to IEC specification.

Hexagonal ferrites or hexaferrites are a family of ferrites with hexagonal crystal structure. The most common member is BaFe12O19, also called barium ferrite, BaM, etc. BaM is a strong room-temperature ferrimagnetic material with high anisotropy along the c axis. All the hexaferrite members are constructed by stacking a few building blocks in a certain order.

References

  1. 1 2 3 Pullar, Robert C. (2012). "Hexagonal ferrites: A review of the synthesis, properties and applications of hexaferrite ceramics". Progress in Materials Science . 57 (7): 1191–1334. doi:10.1016/j.pmatsci.2012.04.001. ISSN   0079-6425.
  2. 1 2 Cao, H.B.; Zhao, Z.Y.; Lee, M.; Choi, E.S.; McGuire, M.A.; Sales, B.C.; Zhou, H.D.; Yan, J.-Q.; Mandrus, D.G. (1 June 2015). "High pressure floating zone growth and structural properties of ferrimagnetic quantum paraelectric BaFe12O19". APL Materials. 3 (6): 062512. arXiv: 1503.02568 . Bibcode:2015APLM....3f2512C. doi: 10.1063/1.4922934 . S2CID   98312433.
  3. ↑ Guillissen, Joseph; van Rysselberghe, Pierre J. (1931). "Studies on zinc and barium ferrites". J. Electrochem. Soc. 59 (1): 95–106. doi:10.1149/1.3497845. S2CID   97566562.
  4. 1 2 3 4 5 Watson, Mark L.; Beard, Robert A.; Kientz, Steven M.; Feebeck, Timothy W. (2008). "Investigation of Thermal Demagnetization Effects in Data Recorded on Advanced Barium Ferrite Recording Media". IEEE Trans. Magn. 44 (11): 3568–3571. Bibcode:2008ITM....44.3568W. doi:10.1109/TMAG.2008.2001591. S2CID   22303270.
  5. ↑ Rowley, S.E.; Chai, Yi-Sheng; Shen, Shi-Peng; Sun, Young; Jones, A.T.; Watts, B.E.; Scott, J.F. (17 May 2016). "Uniaxial ferroelectric quantum criticality in multiferroic hexaferrites BaFe12O19 and SrFe12O19". Scientific Reports. 6 (1): 25724. Bibcode:2016NatSR...625724R. doi:10.1038/srep25724. ISSN   2045-2322. PMC   4869023 . PMID   27185343.
  6. ↑ Goto, Yasumasa; Takada, Toshio (1960). "Phase diagram of the system BaO-Fe
    2    O
    3    ". J. Am. Ceram. Soc. 43 (3): 150–153. doi:10.1111/j.1151-2916.1960.tb14330.x.
  7. ↑ Niazi, Shahida B. (2016). "Solvothermal / hydrothermal synthetic methods for nanomaterials". In Khan, Sher Bahadar; Asiri, Abdullah M.; Akhtar, Kalsoom (eds.). Nanomaterials and their Fascinating Attributes. Development and Prospective Applications of Nanoscience and Nanotechnology. Vol. 1. Bentham Science Publishers. pp. 181–238. ISBN   9781681081779.
  8. ↑ Heck, Carl (1974). "Ceramic magnet materials (ferrites)". Magnetic Materials and Their Applications. Butterworths. pp. 291–294. ISBN   9781483103174.
  9. 1 2 Okazaki, Chisato; Mori, Saburo; Kanamaru, Fumikazu (1961). "Magnetic and crystallographical properties of hexagonal barium mono-ferrite, BaO•Fe
    2    O
    3    ". J. Phys. Soc. Jpn. 16 (3): 119. doi:10.1143/JPSJ.16.119.
  10. ↑ "Characteristics of ferrite magnets". e-Magnets UK. Retrieved 8 December 2013.
  11. ↑ "Barium ferrite: Overview". Fujifilm. Archived from the original on 13 August 2017. Retrieved 13 August 2017.
  12. ↑ Honey, Gerard (2000). "Card-based identification systems". Electronic Access Control. Newnes. pp. 47–55. ISBN   9780750644730.
  13. ↑ "Hard ferrite (ceramic) magnets". Magnaworks Technology. Archived from the original on 20 October 2018. Retrieved 8 December 2013.
  14. 1 2 "Barium ferrite: Overview". Data storage. Fujifilm Technologies. United States: Fujifilm.
  15. ↑ "FujiFilm barium-ferrite magnetic tape establishes world record in data density: 29.5 billion bits per square inch" (Press release). Fujifilm. 22 January 2010. Archived from the original on 19 October 2020. Retrieved 12 October 2020.
  16. ↑ "Barioferrite". mindat.org.
  17. ↑ "List of Minerals". ima-mineralogy.org. 21 March 2011.
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