Which of the following substances has relative magnetic permeability \({\mu }_{\mathrm{r}}≫1\) ?

Relative magnetic permeability (\(\mu_r\)) is a measure of how much a material can become magnetized in an applied magnetic field compared to vacuum. When \(\mu_r \gg 1\), it indicates that the material is highly magnetic, typically found in ferromagnetic materials. Examples of substances with \(\mu_r \gg 1\) include iron, cobalt, and nickel.