Here's the bit that sort of explains things:

"For more than 100 years, physicists generally divided collinear magnets into two fundamental categories: ferromagnets and antiferromagnets.

Ferromagnets have an overall magnetic alignment that produces a net magnetization. These materials are essential to many magnetic memory technologies used today. In conventional antiferromagnets, opposing magnetic moments cancel one another, leaving no overall magnetization and producing electronic behavior very different from that of ferromagnets.

Altermagnetism introduces a surprising third possibility.

Like antiferromagnets, altermagnets have magnetic moments that cancel out, resulting in no net magnetization. However, their electrons can exhibit properties previously associated with ferromagnets.

This unusual combination allows altermagnets to support electrical currents with strongly polarized electron spins while also displaying extremely rapid magnetic dynamics. Those characteristics could make them valuable for a new generation of spintronic devices, potentially advancing the speed and capabilities of future information technologies."