"磁场范围" can be translated into English as "magnetic field range" or "the extent of the magnetic field".
"Magnetic field range" is a more concise and commonly used expression, directly referring to the spatial or intensity limits within which the magnetic field exists or is effective.
"The extent of the magnetic field" provides a slightly more descriptive phrase, emphasizing the boundaries or coverage of the magnetic field.
Both expressions are correct and can be used depending on the context and desired level of detail.