  Geometrically frustrated magnetism is commonly studied in triangular and
Kagome lattices. A rare lattice which exhibits frustration is obtained by
depleting 1/7 of the sites from a triangular lattice and is called a maple-leaf
lattice. We report the magnetic properties of an oxide material with a
maple-leaf lattice: Na2Mn3O7. Structural studies suggest slight lattice
distortion and density functional theory predicts energetic near-degeneracy
between ferromagnetism and antiferromagnetic phases which points towards
competing magnetic orderings at low temperatures. In addition, from our
magnetic studies, we discovered a non-equilibrium spin state below ~50 K. The
bifurcation of field-cooled and zero-field-cooled magnetization curves,
hysteresis of ~16 kOe at 2 K, and time-dependent magnetization response is
consistent with a spin glass state. To our knowledge this is the first report
of such a state in materials with a MLL. This is a promising discovery towards
using spin glass to transport angular momentum or spins for applications low
power spintronics.
