Hard
Substances that can be permanently magnetised are known as magnetically hard. They retain their magnetic properties for a long period of time (sometimes permanently) and they are hard to de-magnetise. These are often alloys of iron, nickel and cobalt.
Soft
Substances that can only be temporarily magnetised are known as magnetically soft. They lose all its magnetic properties very quickly (almost as soon as they leave a magnetic field). Alloys with less iron, nickel or cobalt will be magnetically soft and have a weaker magnetic field.
Kinda random note that doesn't really fit anywhere but we need to know: Alloys of iron are called ferrous and those without iron are called non-ferrous.
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