As for how to safely store the card, Apple is advising customers store it in some container made of soft material — but not leather — and to make sure it doesn't come into contact with any loose metal objects (and of course magnets, as that could demagnetize the strip).
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Cassette demagnetizers of the "cassette" type physically resemble a cassette tape shell but contain circuitry to demagnetize the tape heads of the tape deck. Another type of demagnetizer, the "wand" type can demagnetize anything that it is brought into contact with, including the tape heads and capstans. Nakamichi manufactured a "wand" type demagnetizer in the 1980s. This design had the advantage that it could be used to demagnetize other metal parts of the tape path (not just the actual record/playback heads) however it required careful use (to avoid increasing the magnetization of the heads) and if used too close to actual cassette tapes could inadvertently act as a "bulk eraser".
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The Port of Illahee community dock was built around 1916 to serve the Puget Sound Mosquito Fleet. In later years this port was used by the United States Navy to demagnetize ships.
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Viscous Circle is a story about a strange and inhuman race of beings and an experimental attempt to transfer into creatures that seem only slightly sapient. They are ultimate pacifists that take the form of magnetic disks that float through space and simply demagnetize and destroy themselves when faced with an unpleasant thought.
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During manufacture the materials are subjected to various metallurgical processes in a powerful magnetic field, which aligns the crystal grains so their "easy" axes of magnetization all point in the same direction. Thus the magnetization, and the resulting magnetic field, is "built in" to the crystal structure of the material, making it very difficult to demagnetize.
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Ferromagnetism is very important in industry and modern technology, and is the basis for many electrical and electromechanical devices such as electromagnets, electric motors, generators, transformers, and magnetic storage such as tape recorders, and hard disks, and nondestructive testing of ferrous materials. Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do. Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them very hard to demagnetize. To demagnetize a saturated magnet, a certain magnetic field must be applied, and this threshold depends on coercivity of the respective material.
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Magnetic hysteresis occurs when an external magnetic field is applied to a ferromagnet such as iron and the atomic dipoles align themselves with it. Even when the field is removed, part of the alignment will be retained: the material has become magnetized. Once magnetized, the magnet will stay magnetized indefinitely. To demagnetize it requires heat or a magnetic field in the opposite direction.
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Magnetocrystalline anisotropy has a great influence on industrial uses of ferromagnetic materials. Materials with high magnetic anisotropy usually have high coercivity, that is, they are hard to demagnetize. These are called "hard" ferromagnetic materials and are used to make permanent magnets. For example, the high anisotropy of rare-earth metals is mainly responsible for the strength of rare-earth magnets.
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The length of the arrow shows its magnetization and its width shows its coercivity. The easy axis is assumed to be in the vertical direction. From left to right in Figure 3, an external field is first applied in an upward direction in order to saturate the magnet. Then, the external field is reversed and starts to demagnetize the magnet.
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To demagnetize a saturated magnet, a certain magnetic field must be applied, and this threshold depends on coercivity of the respective material. "Hard" materials have high coercivity, whereas "soft" materials have low coercivity. The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces. The local strength of magnetism in a material is measured by its magnetization.
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In order for a train to launch, the train must "drift" back to "hook" on to a catch car. Twenty-four volts are used to demagnetize a pin underneath the third car, which causes it to drop. At the same time, two bellows actuators fill up with air. Meanwhile, near the back of the train, two drive tires that are holding the train in place begin to retract.
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Videotapes may be stored in polypropylene cases, but without paper inside the cases and "magnetic media should never be stored at temperatures below 46 degrees Fahrenheit". Magnetic media should also be kept away from magnetic sources, which could demagnetize them. Optical digital media - DVDs and CDs are another media that will need storage space. Optical media should be stored in hard plastic jewel cases or other inert plastic containers; avoid storage in plastic sleeves.
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During the Second World War, Bitter worked for the Naval Bureau of Ordnance. He often traveled to England to find ways to demagnetize British ships to protect them from a new type of German mine, which used a compass needle to trigger detonation. The mine, dropped from the air, would sink to the bottom of a river and remain there with its magnetic needle aligned to the Earth's magnetic field at that location. When a ship passed over it, the mass of the ship caused the magnetic needle to move slightly.
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When the temperature of the sample was close to its TC it was possible to turn the ferromagnetism on or off by applying a gate voltage which could change the TC by ±1°K. A similar transistor device was used to provide further examples of gateable ferromagnetism. In this experiment the electric field was used to modify the coercive field at which magnetization reversal occurs. As a result of the dependence of the magnetic hysteresis on the gate bias the electric field could be used to assist magnetization reversal or even demagnetize the ferromagnetic material.
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A stack of ferrite magnets A ferrite is a ceramic material made by mixing and firing large proportions of iron(III) oxide (Fe2O3, rust) blended with small proportions of one or more additional metallic elements, such as barium, manganese, nickel, and zinc. They are electrically nonconductive, meaning that they are insulators, and ferrimagnetic, meaning they can easily be magnetized or attracted to a magnet. Ferrites can be divided into two families based on their resistance to being demagnetized (magnetic coercivity). Hard ferrites have high coercivity, so are difficult to demagnetize.
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Demagnetizers contain electronic circuitry and require a power source — either a battery or a power cord. A third design consisted of a cassette shell with a head cleaning tape wound on the spools and a disc shaped magnet mounted above the head cleaner tape such that when the play button was activated the head cleaner physically cleaned the head surface and simultaneously made the magnet rotate, creating the alternating magnetic field required for demagnetizing. Some cassette deck manufacturers even produced decks with a self-demagnetize button. These worked by feeding the record head with a strong high frequency signal, which was gradually reduced in amplitude to zero over a few seconds.
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The chassis, frame, or basket, is designed to be rigid, preventing deformation that could change critical alignments with the magnet gap, perhaps allowing the voice coil to rub against the magnet around the gap. Chassis are typically cast from aluminum alloy, in heavier magnet-structure speakers; or stamped from thin sheet steel in lighter-structure drivers. Other materials such as molded plastic and damped plastic compound baskets are becoming common, especially for inexpensive, low- mass drivers. Metallic chassis can play an important role in conducting heat away from the voice coil; heating during operation changes resistance, causes physical dimensional changes, and if extreme, broils the varnish on the voice coil; it may even demagnetize permanent magnets.
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These motors are relatively costly, and are used where exact speed (assuming an exact-frequency AC source) and rotation with low flutter (high-frequency variation in speed) are essential. Applications included tape recorder capstan drives (the motor shaft could be the capstan), and, before the advent of crystal control, motion picture cameras and recorders. Their distinguishing feature is their rotor, which is a smooth cylinder of a magnetic alloy that stays magnetized, but can be demagnetized fairly easily as well as re-magnetized with poles in a new location. Hysteresis refers to how the magnetic flux in the metal lags behind the external magnetizing force; for instance, to demagnetize such a material, one could apply a magnetizing field of opposite polarity to that which originally magnetized the material.
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These include the elements iron, nickel and cobalt and their alloys, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism. Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do. Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them very hard to demagnetize.
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A third, single retractor cable is attached to the rear of the catch-car, it runs around a pulley wheel at the rear end of the launch track and returns to the hydraulic building along the bottom of the launch track, where it is wound in the opposing direction on the winch's drum. The train connects to the catch-car with a solid piece of metal known as a "launch dog" that drops down from the center car. The launch dog is normally retracted and is held in place by a small magnet, but the launch area has electrical contacts that demagnetize the magnet and cause the launch dog to drop down. The launch dog drops down at an angle, similar to the chain dog that a lifted coaster uses to connect to the lift chain.
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In the previous process, when the magnetic moments in the hard magnet start to rotate, the intensity of external field is already much higher than the coercivity of the soft phase, but there is still a transition region in soft phase. If the thickness of the soft phase is less than twice as thick as the transition region, the soft phase should have a large effective coercivity, smaller than but comparable to the coercivity of the hard phase. Figure 4: Magnetic moments around thin soft phase In a thin soft phase, it is hard for the external field to rotate the magnetic moments, similar to a hard magnet with high saturation magnetization. After applying a high external field to partially demagnetize the magnetic moments in the hard phase and after subsequently removing the external field, the rotated moments in the soft phase can be rotated back by exchange coupling with the hard phase (Figure 5).
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