Magnetic Properties and Materials

The following sections are included:

• Introduction

• Fundamentals

  • Magnetic flux and permeability

  • Basic units

  • Magnetisation and relative permeability

  • Magnetic susceptibility

  • The origin of magnetism, Bohr magneton

  • Types of magnetism

    • Diamagnetism

    • Paramagnetism

    • Ferromagnetism

    • Electron structure and magnetic behaviour

    • Antiferromagnetism

    • Ferrimagnetism

  • Effect of temperature on ferromagnetism - Curie Point

  • Ferromagnetic anisotropy and magnetostriction

    • Ferromagnetic anisotropy

    • Magnetostriction

    • Ferromagnetic domains and domain movement

      • Ferromagnetic domains

      • Domain movement during magnetisation

  • Magnetic energy and domain structure - Types of energy that determines the structure of domains

    • Magnetic exchange energy

    • Magnetostatic energy

    • Magnetocrystalline anisotropy energy

    • Domain wall energy

    • Magnetostriction energy

  • Magnetisation and demagnetisation of magnetic materials, hysteresis loop

  • Energy losses in magnetic materials

    • Hysteresis losses

    • Material factors

    • Eddy current energy losses

• Soft Magnetic Materials

  • Iron-silicon alloys

  • Effect of the addition of 3-6%Si to Fe

  • Ni-Fe alloys (permalloy)

  • Amorphous alloys (metallic glasses)

  • Nanocrystalline materials

• Hard Magnetic Materials

  • Maximum energy product, (BH)_max

  • Alnico alloys

  • Rare earth alloys

    • Nd-Fe-B alloys

    • Sm-Co alloys

  • Other materials

  • Applications

• Ferrites – Ceramic Magnetic Materials

  • Soft ferrites

  • Hard ferrites

  • A summary - “hard” and “soft” materials

• Dilute Magnetic Semiconductor (DMS)

• Case Study – Materials in Magnetic Recording

  • Magnetic recording principle

  • Recording heads

  • Recording medium

  • Tape and disc processing

  • Storage density