  Improved constraints on exotic spin-dependent interactions are established at
the micrometer scale by a magnetometer with ensembles of nitrogen-vacancy (NV)
centers in diamond. A thin layer of NV electronic spin ensembles is utilized as
the sensor, and a lead sphere is taken as the source of the nucleons. The
exotic spin-dependent interactions are explored by detecting the possible
effective magnetic fields by the sensor. Stringent bounds on an exotic
parity-odd spin- and velocity-dependent interaction are set within the force
range from 5 to 500 $\mu$m. The upper limit of the corresponding coupling
constant, $g_A^eg_V^N$, is improved by more than three orders of magnitude at
330 $\mu$m. Improved constraints of $P, T$-violating scalar-pseudoscalar
nucleon-electron interactions, are established within the force range from 6 to
45 $\mu$m. The limit of the corresponding coupling constant, $g_S^Ng_P^e$, is
improved by more than one order of magnitude at 30 $\mu$m. Our result shows
that a magnetometer with a NV ensemble can be a powerful platform for probing
exotic spin-dependent interactions.
