Card coercivity is a measurement of magnetic force strength when coding access cards. Any magnetic badges will need to have their own unique data encoded onto the metal stripe on the back, but not every card is modified in the same way — they can have either low or high coercivity. Card magnetism is measured in units called oersteds. Cards with low coercivity are encoded at around 300 oersteds and are often used for purposes like hotel room keys. Cards with high coercivity are encoded at much higher levels, around 3,300 oersteds, and are often used for things like credit cards.
High coercivity cards are much less likely to be affected by outside magnetic fields, like ones generated from your phone, but they require more data. For visitor badges, you might want to opt for low coercivity cards because the badges might not come back to you. For almost every other use, especially employee access badges, it is recommended that you opt for high coercivity cards because they last much longer and will cause fewer access issues down the line.