tweaking location of xlabel

Hello,

When I output my figures to postscript format the xlabel and ylabel are
a bit clipped. I'm trying to tweak the position of the xlabel using:

f=figure(0, figsize=(3,3))
[...]
contour(r, r, x, [0.5, 0.6, 0.7, 0.8, 0.9], colors='k')
xlabel("magnitude", fontsize="10")
ylabel("differential", fontsize="10")
f.get_axes()[0].get_xaxis().get_label().set_position((0.5,5)) # I tried
y's of 0.1 to 5.0

But the xlabel doesn't move one bit. Any suggestions on how I move the
xlable or otherwise fix the clipping?

I just started using matplotlib and I am very impressed. Thanks to the
developers!

best,
Jeff O'Neill