Surface and Interface Magnetism Using Radioactive Probes -- The Ferromagnetic Semiconductor HgCr2Se4 as Investigated with Different Nuclear Probes by the PAC Method -- The Role of Nuclear Nanoprobes in Inducing Magnetic Ordering in Graphite -- Heavy Ion Irradiated Ferromagnetic Films: The Cases of Cobalt and Iron -- Exchange Interactions and Curie Temperatures in Dilute Magnetic Semiconductors …