Applications 14

14.1 Introduction

14.2 Electrical Steels (Soft Magnetic Materials) Electrical steel is used to multiply the magnetic flux in the cores of electromagnetic coils – transformers, electro-motors, generators, electromagnets. - Highest possible permeability, and easily magnetize and demagnetize it. 14.2.1 Core Losses : The energy that is dissipated in the form of heat within the core of electromagnetic devices when the core is subjected to an alternating magnetic field Eddy current loss Hysteresis loss

In order to decrease the eddy current, The core can be made of an insulator – use ferrites The core can be made from pressed iron powder whereby each powder is covered by an insulating coating.- decrease in s resulted in large decrease in m Made out of thin sheets which are electrically insulated from each other

14.2.2 Grain Orientation Magnetic Anisotropy Easy Direction The magnetic properties of Crystalline ferromagnetic materials depend on the crystallographic direction in which an external field is applied Magnetization curves of single crystals If the external field is applied in the <100> direction, saturation is achieved with the smallest possible field strength Easy Direction

14.2.3 Composition of Core Materials Low carbon steel : The least expensive core material -> relatively small permeability, higher core losses than grain-oriented silicon iron Iron-silicon alloys : higher permeability and a lower conductivity than low carbon steel, heat treatments of these alloys can be performed at much higher temperatures without interference from phase changes during cooling Permalloy, Supermalloy, Mumetal : The highest permeability (multicomponent nickel based alloys) 14.2.4 Amorphous Ferromagnets - a considerably higher permeability and a lower coercivity - electrical resistivity is generally larger

14.3 Permanent Magnets (Hard Magnetic Materials) : Devices that retain their magnetic field indefinitely. Hard magnetic materials Demagnetization curve Maximum energy product

Demagnetizing Curve

14.4 Magnetic Recording and Magnetic Memories