Ancient Greeks and Chinese found in nature a kind of natural magnetized stone, called "magnetite." This stone can magically suck up a small piece of iron, and always swing in the same direction. Early voyagers identified the direction of the magnet as the earliest compass at sea. After thousands of years of development, today's magnet has become a powerful material in our life. Through the synthesis of different materials alloy can reach the same effect with the magnetite, but also can improve the magnetic force. Artificial magnets appeared in the 18th century, but the process of making stronger magnetic materials was slow until the Alnico was made in the 1920s. Ferrite was subsequently made in the 1950s, and rare earth magnets were made in the 1970s [Rare Earth magnets including NdFeB and SmCo]. At this point, magnetic technology has been rapid development, the magnetic material also makes the components more miniaturized. Most magnetic materials can be magnetized in the same direction to saturation, a direction called "magnetization direction" (orientation). Magnets without orientation (also called isotropic magnets) are much weaker than magnets with oriented magnets (also called anisotropic magnets).