  We describe a single beam compact Spin Exchange Relaxation Free(SERF)
magnetometer whose configuration is compatible with the silicon-glass bonding
micro-machining method. A cylindrical vapor cell with 3mm diameter and 3mm in
length is utilized in the magnetometer. In order to reduce the wall relaxation
which could not be neglected in micro-machined SERF magnetometer, 3
Amagats(1Amagat=2.69$\times$ 10$^{19}$/cm$^3$) neon buffer gas is filled in the
vapor cell and this is the first demonstration of a Cs-Ne SERF magnetometer. We
also did a simulation to show that neon is a better buffer gas than nitrogen
and helium which is typical utilized in vapor cells. In order to reduce the
laser amplitude noise and the large background detection offset which is
reported to be the main noise source of a single beam absorption SERF
magnetometer, we developed a laser power differential method and a factor of 2
improvement of the power noise suppression has been demonstrated. Finally, we
did an optimization of the magnetometer and sensitivity of 40$fT/Hz^{1/2}$@30Hz
has been achieved.
