I'm reading about the Stern Gerlach experiment in Sakurai's well-known book "Modern Quantum Mechanics". I remember studying this years ago, and somehow back then this question didn't enter my mind. However, I can't seem to figure out the answer. I understand that a gradient in magnetic field can produce a force on the magnetic moment and split the beam of silver atoms into spin-up and spin-down. Sakurai describes how the beam is composed of randomly oriented atoms, and hence "there is no preferred direction for the orientation of the magnetic moment". However, what confuses me is that I would expect the presence of the magnetic field to also put a torque on the magnetic moment. Why isn't there a torque that tries to orient the spin and give a bias to one of the two spin states?