Planetary Magnetic Fields

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I'm looking for a bit of insight here, and I thought who better to ask than my fellow Aspies on here, where I will almost certainly find someone far more knowledgeable than myself on any given subject. I'm in college, training to become an Electromechanical Technician, and those of you who have taken similar courses will probably have had a lecture or two on magnetism. Magnetism in itself is an incredibly fascinating subject, but a couple key points brought up in the lecture really got my brain going. The first of which is that Earth has a magnetic field, which (as the lecturer stated) was projected from the Earth's mainly Iron core. Without the field, the Earth's atmosphere would be vaporized in a powerful barrage of Alpha particles being cast off from the sun. And most importantly, evidence suggests that our neighbor, Mars, once had a magnetic field, and an atmosphere, but lost the field and the atmosphere followed suit.

Point two brought up in the lecture: Heat dissipates magnetism. The hotter something is, the less magnetic it is, and while we were not given a formula of the relationship of between magnetism and heat, I would be surprised if one did not exist.

From these two points, I started drawing lines. The Earth's core is incredibly hot, how is it then that we are able to maintain our magnetic field?
On that topic, as I last understood, Mars is fairly geologically inactive, meaning that it's core SHOULD be colder than the Earth's. If that is the case, why did Mar's magnetic field collapse? From my understanding it should be far more powerful than the Earth's field, and should be able to protect it's atmosphere from the effects of solar wind.

I look forward to hearing some answers and some good educated guesses that can help put my questions on this topic to rest.

As far as I know, earths magentic field is the result of the convective movements of the Earth's core and the earth rotation itself. This movement produces electric currents which, as you might know produce a magnetic field.

When it comes to magnets, most of them consist of individual particles, every particle has its own magnetic field. A magnet is a material or compound in which it's individual particles have their magnetic field vectors alligned or mostly alligned. All those fields being "added up" you get to see a macroscopic magnet. When you apply heat to a magnet, you are actually increasing the amount of kinetic energy in all its individual particles, which leads to misalignment of the magnetic field vectors. As a result, the magnetic field is "weakened" since all its individual smaller "magnet particles" aren't alligned.

The point is that while magnetism in magnets is produced by the allignment of the magnetic field vectors of every individual particle of the magnet, earth's magnetism is the result of an electric current that is the result of the earth's high core activity. Both mechanisms are different and therefore, heat has different effects in both, since heat actually increases the earth's core activity.

Since Mars has a cooler core, it is less active, if the core is not active enough, the conditions aren't met to support a magnetic field, and therefore it collapsed.

Thank you for that, that makes a lot more sense. It seems that all of those questions were a result from misinformation from the lecturer, having the Earth work like an electromagnetic clears up some other questions I had in the back of my mind, such as pole flip which to my knowledge has not been observed in lodestones. (Meaning a singular lodestone has never, to my knowledge, inverted its north and south pole by means other than physically turning.)

Ferromagnetism of the type found in permanent bar magnets is indeed diminished in a bar magnet after it has been heated.

This flow of liquid iron inside our spinning planets core generates electric currents, which in turn produce magnetic fields, so the earth is a generator, whereas a bar magnet acts more like a battery.
One point of explanation remains how spinning currents in molten fluid can create a stable and imperceptibly moving polar axis, but the theory is strong enough regardless.

On a side note, the sun is hotter than the earth's core and it generates a massive magnetic field by comparison.