Magnetic steels: alloying element that raises residual magnetism and coercive force Identify the alloying element most effective for increasing both remanence (residual magnetism) and coercivity in steels used for permanent magnets. Choose the correct option.

Given
Selection of an alloying element for steel magnets that increases both residual magnetism (remanence) and coercive force.

Concept / Approach
Cobalt additions in magnetic steels (e.g., Alnico-type alloys) increase saturation magnetization, improve remanence, and raise coercivity, making the steel suitable for permanent magnets. Nickel typically improves permeability but not coercivity to the same extent; chromium and vanadium have other primary roles (hardenability, grain refinement, secondary hardening).

Option analysis
• Chromium: more for corrosion resistance/hardenability; not the best for coercivity + remanence together.
• Nickel: improves toughness/permeability; not the strongest effect on coercivity.
• Vanadium: strong carbide former; improves wear resistance and secondary hardening.
• Cobalt: boosts remanence and coercivity.

Final Answer
Cobalt