Magnetic media paramagnetic

The tendency of the magnetic lines of force to pass through a medium relative to their tendency to pass through a vacuum is the magnetic permeability, p. This is one of the parameters that distinguishes a diamagnetic material from a paramagnetic substance. Permeability is defined as. 

Fig. 9 Magnetization curves for various ZFS systems modeled as a powder average at T = 4.2 K top panel D/k = -5 (solid), - 10 (long dashed), - 15 (medium dashed),- 20 K (short dashed) bottom panel D/k = + 5 (solid), + 10 (long dashed), + 15 (medium dashed), + 20 K (short dashed) Brillouin function for a Curie paramagnet - dot-dashed...

The lifetimes given above relate to positronium in vacuum. In the medium a new possibility of destruction appears the positron bound in Ps can annihilate with one of strange electrons having appropriate (opposite) spin orientation. The process is called pick-off and leads to two quantum annihilation. If the medium is paramagnetic, another process shortening the o-Ps lifetime is possible the interaction with magnetic moments can transform o-Ps into p-Ps, which decays almost immediately (conversion process). Both e and Ps can participate in chemical reactions with molecules of the medium changing the Ps formation probability... 

Fig. 8.1. Molar magnetisation versus magnetic field for paramagnets (a) for T = 4.2 K individual curves correspond to S = 1/2 (solid), 1 (long dashed), 3/2 (medium dashed), 2 (short dashed) and 5/2 (dotted) (b) for S = 5/2 individual curves correspond to T = 4.2 K (solid), 77 K (long dashed) and 300 K (medium dashed).

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