In some part of a magnet wouldn‘t find particles with both positive and negative fields between both poles?
The magnetic field is produced by negatively charged particles - electrons. Posively charged particles - protons - are not involved in the creation of a magnetic field of magnetized solids. When a charged particle moves in a certain way, it creates a magnetic field, and there are some materials in which this effect of the electrons can be aligned to give us magnetic materials. in a magnet, the alignment of the fields does not change in the magnet. As a very rough analogy, you could think of a series of water pumps, one pumping into the next, and the next and so forth. Water would enter at one end, and emerge at the other. So you could see one side of the pump system as 'negative' and the other side as 'positive'. But clearly, there would not be a point in the middle that was niether negative nor positive. Each pump would pump in exactly the same way. A magnet is very rougly like that. Each group of molecules, called a domain, is magnetized in a certain direction, and when many domains are in the same direction, you have a magnet.
