Neutron diffraction and small angle neutron scattering measurements have be
en carried out on RNiBC (R=Er, Th, Dy) to investigate the crystallography,
magnetic correlations, and long range magnetic ordering. Crystallographic r
efinements show a strong boron-carbon and nickel-carbon bonding similar to
RNiZB2C, but the rare-earth-carbon plane exhibits a buckling which does not
exist in the RNi2B2C series. The magnetism in the RNiBC series is quite si
mple, with a magnetic moment direction going from the a-b plane to the c ax
is as the atomic number of the rare-earth increases. Er becomes ferromagnet
ic at T-C= 4.6 K, with a saturated moment of 7.2 mu (B) along the c axis. T
h orders ferromagnetically at T-C= 15 K. Below 12.5 K an incommensurate mod
ulation develops with a modulation wave vector of (0 0 1/8), as well as an
antiferromagnetic component with k= (0 0 1/2). The moments, which vary in b
oth magnitude and direction, are in the a-b plane with an average value of
7.79 mu (B). DyNiBC exhibits the same behavior, with a T-C and T-N of 17.5
and 13.5 K, respectively.