Final answer:
The subject of this question is Chemistry. A hard magnetic metal used in the production of steel is called a ferromagnetic material. In cancer treatment, a radioactive form of an element called cobalt-60 is used.
Step-by-step explanation:
The subject of this question is Chemistry. A hard magnetic metal used in the production of steel is called a ferromagnetic material. It maintains a strong magnetic field even after the external magnetic field is removed. One example of a hard magnetic metal is neodymium (NdFeB) which is commonly used in the production of strong permanent magnets.
In terms of cancer treatment, a radioactive form of an element called cobalt-60 is commonly used. It emits gamma rays which can be used to target and destroy cancer cells. Radioactive materials like cobalt-60 are used in radiation therapy to kill cancer cells by damaging their DNA.