Magnets are an integral part of our daily lives, from the simple fridge magnets that hold our grocery lists to the sophisticated electromagnets that power medical imaging machines. The diverse applications of magnets stem from the unique properties of magnetic elements, which have fascinated scientists and laypeople alike for millennia. In this comprehensive guide, we will delve into the world of magnetic elements, exploring their properties, uses, and the fascinating journey from the discovery of iron to the modern-day wonder material, neodymium.
磁気の基礎
To understand magnetic elements, we must first familiarize ourselves with the basics of magnetism. Magnetism is a fundamental property of matter that arises from the motion of electrons within atoms. When electrons orbit around the nucleus of an atom or move through a conductor, they generate a tiny magnetic field. In most materials, these individual magnetic fields cancel out each other, resulting in no net magnetism. However, in certain materials, known as ferromagnetic materials, these individual fields align, creating a strong magnetic field that can attract or repel other magnets.
強磁性
Ferromagnetism is the strongest form of magnetism and is responsible for the magnetic properties of materials like iron, nickel, and cobalt. In ferromagnetic materials, the atomic magnetic moments align parallel to each other, creating regions of aligned atoms called domains. When a ferromagnetic material is subjected to an external magnetic field, the domains align themselves with the field, causing the material to become magnetized. Once the external field is removed, the material retains its magnetization, a phenomenon known as hysteresis.
Diamagnetism, Paramagnetism, and Ferromagnetism
Ferromagnetism is just one of the three main types of magnetism, along with diamagnetism and paramagnetism. Diamagnetism is the weakest form of magnetism, where the magnetic moments of atoms within a material oppose the applied magnetic field. Diamagnetic materials, such as copper, silver, and gold, are weakly repelled by magnets.
Paramagnetism is a slightly stronger form of magnetism, where the magnetic moments of atoms within a material align with the applied magnetic field but quickly lose their magnetization when the field is removed. Paramagnetic materials, such as aluminum, platinum, and oxygen, are weakly attracted to magnets.
The Discovery of Magnetic Elements
The earliest known use of magnets dates back to ancient times, when the ancient Greeks and Chinese discovered that certain naturally occurring rocks, later identified as magnetite (Fe3O4), could attract iron objects. The word “magnet” itself is derived from the ancient Greek term “magnetite lithos,” meaning “lodestone.”
The discovery of other magnetic elements, such as nickel and cobalt, came much later. Nickel was first isolated in 751 AD by the German alchemist and monk, St. Albertus Magnus, while cobalt was identified as a distinct element by the Swedish chemist, Torbern Bergman, in 1755. These elements, along with iron, form the basis of ferromagnetic materials that are widely used today.
Iron: The Pioneer Magnetic Element
Iron (Fe) is perhaps the most well-known and historically significant magnetic element. It is also the most abundant ferromagnetic element, making up about 5% of the Earth’s crust. Iron’s unique combination of high