I assume your geometry and voltage are fixed, and the only thing you are changing is the core material.
Voltage applied,, number of turns, cross section etc all remain the same.
Compare the case of two different materials with different permeabilities (mu)
(Higher mu means higher B vs H curve)
Volts per turn is constant, established by the supply voltage and the number of turns.
That means flux is the same in either case.
Reluctance R = Area*PathLength/mu.
The only thing you changed is me. So reluctance R is lower for the higher mu
NOW, we go to UKPete's magnetic circuit equation:
flux = mmf / reluctance
We said flux is constant and reluctance is lower (for the higher mu). That means mmf is lower (for the higher mu.) In physical terms, the higher mu material does a better job at limiting exciting current.
In the context of your whole design, the reduced exciting current may give you additional thermal margin which allows you to wrap more turns which gives you higher flux and force. But if you change only material and not turns, voltage etc you don’t a higher force (neglecting resistive losses etc).
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