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Ferromagnetic Materials

Ferromagnetic Materials

Introduction

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    Due to the application of a magnetic field, ferromagnetic materials tend to exhibit or display significant magnetism in the field direction. Magnetism in these materials is principally caused by the alignment patterns of their constituent atoms. These atoms resemble elementary electromagnets in their behaviour. Ferromagnetic compounds are extremely rare. Iron, cobalt, nickel, and most of their alloys, as well as several rare earth metal complexes, are the most frequent. Ferromagnetic materials are extensively utilised in cassettes, hard drives, and other nonvolatile data storage devices. Because of the interaction of electric current and light with magnetic order, they are also employed for information processing.

    Ferromagnetism‘s Causes

    Atomic dipoles in small regions called domains in an unmagnetized ferromagnetic material are aligned in the same direction. Even in the absence of an external magnetising field, the domains have a net magnetic moment.

    Neighboring domains have magnetic moments that are oriented in opposite directions. Because they cancel each other out, the material’s net magnetic moment is zero. These domains all align in the direction of the applied magnetic field when an external magnetic field is applied. The material becomes strongly magnetized in a direction parallel to the magnetising field as a result of this process.

    Ferromagnetic materials

    Due to the application of a magnetic field, ferromagnetic materials tend to exhibit or display significant magnetism in the field direction. Magnetism in these materials is principally caused by the alignment patterns of their constituent atoms. These atoms resemble elementary electromagnets in their behaviour.

    Metals make up the majority of ferromagnetic compounds. Iron, Cobalt, Nickel, and other ferromagnetic materials are examples. Metallic alloys and rare-earth magnets are also ferromagnetic materials.
    Magnetite is a ferromagnetic substance made from iron oxide. The temperature of the Curie point is 580°C. It was once thought to be a magnetic material. Among all the natural minerals on the planet, magnetite possesses the highest magnetism.

    Properties of Ferromagnetic Materials

    • The atoms of ferromagnetic materials exhibit a permanent dipole moment in domains.
    • Atomic dipoles in ferromagnetic materials are aligned in the same direction as the external magnetic field.
    • The magnetic dipole moment is large and orientated in the direction of the magnetising field.
    • The magnetization intensity (M) is extremely high and positive, varying linearly with the magnetising field (H). As a result, the type of the substance determines saturation.
    • Magnetic susceptibility is high and positive. Magnetic susceptibility is calculated as Xm = M / H, where M is the magnetization intensity, and H is the applied magnetic field strength.
    • The material’s magnetic flux density will be enormously positive. Inside ferromagnetic materials, magnetic field lines become densely packed. B = 0 (H + M), where 0 is the magnetic permittivity of free space, H is the applied magnetic field strength, and M is the magnetization intensity.
    • The relative permeability is also quite high and varies linearly with the magnetising field, despite the fact that the magnetic field inside the material is significantly stronger than the magnetising field.
    • They have a tendency to cause the material to pull in a huge number of force lines.
    • The field has a high attraction to ferromagnetic substances. As a result, in a non-uniform field, they gravitate to the poles, where the field is strongest.
    • Because the field is strongest at the poles, ferromagnetic powder gathers on the sides and displays depression in the middle when placed in a watch glass on two pole pieces that are sufficiently spaced.
    • Because of the increasing temperature, a ferromagnetic substance loses its ferromagnetic characteristics.

    Hysteresis

    When the external magnetic field is removed, a ferromagnetic substance does not completely demagnetize. A magnetic field in the opposite direction must be supplied to restore the material’s magnetization to zero. Hysteresis is a feature of ferromagnetic materials that allows them to retain their magnetism when an external field is removed.

    Retentivity refers to the magnetic flux density that remains when the magnetizing force is removed.
    The coercivity of a reverse magnetising field is the strength with which it must be applied to demagnetize a material entirely.

    Retentivity is the magnetic flux density that remains when the magnetising force is lowered to zero.
    Coercivity refers to the strength of the reverse magnetising field that must be applied to demagnetize the material completely.

    Curie temperature

    The force of magnetism is determined by the magnetic moment, a dipole moment within an atom that results from the angular momentum and spin of electrons. The Curie temperature is the point at which a material’s intrinsic magnetic moments change direction.

    Magnetic moments align to provide permanent magnetism, and disordered magnetic moments are driven to align in an applied magnetic field to produce induced magnetism. At the Curie temperature, for example, ordered magnetic moments (ferromagnetic, Figure 1) change and became disordered (paramagnetic, Figure 2). Magnets weaken at higher temperatures because spontaneous magnetism occurs only below the Curie temperature. The Curie–Weiss law, which is derived from Curie’s law, can be used to compute magnetic susceptibility above the Curie temperature.

    The temperature of Curie in ferroelectric materials

    Curie temperature (TC) describes the temperature at which a ferroelectric material becomes paraelectric, similar to ferromagnetic and paramagnetic materials. As a result, the temperature at which ferroelectric materials lose their spontaneous polarisation due to a first or second-order phase change is referred to as TC. The Curie Weiss temperature T0, which specifies the maximum of the dielectric constant, is identical to the Curie temperature in the case of a second-order transition. In the event of a first-order transition, the Curie temperature can be 10 K higher than T0.

    Applications

    • Ferromagnetic materials are used in two important technological applications. They are used to develop the nucleus of electromagnetic machines as flux multipliers.
    • Data (magnetic recording) and/or energy preservation (magnets).
    • The applications are used to store nonvolatile data on hard discs, cassettes, and a variety of other devices.
    • Because of the interaction of electric light and power with the magnetic effect, it is used in information processing.
    • Transducers, microphones, and capacitors are equipment that uses this material.
    • It was incorporated in applications that necessitate a high piezoelectric coupling constant.
    • Generators, telephones, loudspeakers, electric motors, and magnetic strips on the rear of debit and credit cards all use this material.

    FAQs

    For ferromagnetic materials, what is the Curie temperature?

    The temperature at which materials lose their ferromagnetic properties can only be kept using external magnetism.

    In ferromagnetism hysteresis, what are retentivity and coercivity?

    When the magnetic force is removed, the object's retentivity refers to its capacity to restore its magnetic nature. The intensity of the magnetic field required to reduce the magnetic nature to zero is referred to as coercivity.

    Is it possible to demagnetize a magnet?

    There are several ways to demagnetize a magnet. They're hotter than they're supposed to be. Place the magnet in a field opposite to what it should be. Magnets should be hammered. Leaving magnets alone for extended periods.

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