Basic Properties of Magnetic Materials：磁性材料的基本性质.docx

Name(s)___________________Basic Properties of Magnetic MaterialsEquipment NeededWasher and various metals, compass, two bar magnetsIntroductionWe will qualitatively study some of the basic properties of magnetic materials.Permanent magnets are materials that retain their magnetic properties for a long time. Materials which can be used to make permanent magnets are called hard magnetic materials. Some magnetic materials are naturally occurring. For example lodestone is composed of magnetite, an iron-bearing mineral and is a naturally occurring permanent magnet. Synthetic magnetic materials which are used to make permanent magnets are usually alnicos: iron alloys containing aluminum, nickel, and cobalt. Some permanent magnets are ferrites made of powdered iron oxide and barium/strontium carbonate ceramics. Permanent magnets generally are described as having north and south poles. When permanent magnets are brought near each other, like poles repel and opposite poles attract.Temporary magnets only act as magnets if they are in the presence of a magnetic field produced by a permanent magnet or an electric current. Magnetic materials from which temporary magnets are made are called soft magnetic materials. Any object that can be lifted or moved by a magnet is a temporary magnet. Objects such as these will eventually lose their magnetism once the permanent magnet is removed. Sometimes the object may retain weak magnetic properties.Non magnetic materials are materials that do not exhibit magnetic properties in the presence of a magnetic field. Pure aluminum is a metal that is non-magnetic. All non-metallic materials are also non-magnetic.Magnetic domains are clusters of aligned atoms in a material. In iron, for example, a magnetized atom will likely cause its neighbors to line up in the same direction, forming a larger field. This forms magnetic domains. The more aligned the domains are, the stronger the magnetic field.ExplorationTemporary magnets Materials which are a