Most people recognize magnets as toys or materials with limited applicability like refrigerator magnets or simple magnets to hold papers when attached to a metal surface. What many people do not know is that in fact magnetic materials (magnets) have a wide range of applications in many areas of our lives like medical services, security devices, communications, transportation and even nowadays magnetic materials are wide use in areas like jewelry where the development of magnetic bracelets and earrings has change the way people conceive magnetism. Here is presented a review of the main applications that magnetic materials have in the modern world and the future applicability of the new types of materials that are produce these days.
Compasses represent a traditional application of magnets. A compass is an instrument use to measure directions using as reference the earth’s magnetic poles. The frame of reference consists of the four cardinal points, north, south, east and west. The magnetic compass interacts with the earth magnetic field, which is like a giant bar magnet, pointing towards the magnetic poles of the earth.
The Chinese were the first to note these phenomena despite their lack of knowledge about the electromagnetic forces that cause this effect. The compass was invented during the Han Dynasty between the second century BC and the first century AD and was only used for navigation by the eleventh century. Later on it was introduced to Europe where was replaced by the dry compass. In the 20th century the liquid-filled magnetic compass was introduced. The invention of the compass was definitely one of the most important creations in the history of humanity.
Magnetic Resonance Imaging (MRI)
MRI is a technique widely use nowadays in medicine for the diagnosis of different diseases like cancer. It main use relies on the construction of images of internal organs of the body avoiding the use of surgery to find and diagnose the disease. Because the body is composed of mainly water molecules, MRI uses the properties of water in the presence of a high magnetic field to produce an anatomical image of specific areas of the body, being especially useful for the imaging of the brain, muscles and the heart. In a MRI device a magnetic field is used to make hydrogen atoms in water molecules resonate at a given frequency and then a radiofrequency pulse is applied changing the energy state of the spins. When the radiofrequency pulse stops, electromagnetic signals are emitted due to the relaxing of the spins; this is detected by the instrument and an image is formed taking advantage of tissue contrast. » Read more: Magnetic Materials