If you want n logarithmically spaced ticks (which would appear linearly spaced on a log plot, you should just set the ticks to be logarithmically spaced. That's pretty easy with logspace:
loglog([1 100],[1 100])
nticks = 4;
yticks(logspace(0,2,nticks))
% note that this is equivalent to yticks(10.^linspace(0,2,4))
grid on
set(gca,'YMinorGrid', 'off', 'YMinorTick', 'off')
The minor ticks are a bit trickier, you can get at them by grabbing the YAxis object
figure
loglog([1 100],[1 100])
nticks = 4;
yticks(logspace(0,2,nticks))
nminorticks = 16;
ax=get(gca,'YAxis');
ax.MinorTickValues=logspace(0,2,nminorticks);
grid on
