The German group GITEC http://gitec-forum.de/ has recently translated from German to English a chapter on AlNiCo magnets from a larger body of work called "Physics of Electric Guitar", which is still mostly only available in German to date. Here's a link to the PDF https://gitec-forum.de/wp/wp-content/uploads/2017/12/PotEG-4.4.1-Alnico-Magnets.pdf This section is rich with information about AlNiCo magnets, including how they're made, why they work the way they do, how they differ from other kinds of metals and permanent magnets, and why AlNiCo can be anistropic or isotropic (oriented). It's rather technical, but it's easy enough to follow, and it serves as a starting point for further googling. It's fairly rare to find such in depth information about AlNiCo for free on the Internet, especially since AlNiCo is all but an obsolete type of permanent magnet this day and age, and for it to be geared towards the study of guitar pickups is a double plus, with some interesting pickup history mixed in with the technical details of AlNiCo. There is even an interesting quote from Seth Lover (though keep in mind it was translated to German and then back to English again) in which he claims his preference was for AlNiCo 5, though for technically stated reasons, not tonal reasons.