139 La NQR study of antiferromagnetic La2NiO4+δ and La2CoO4−δ

139 La NQR study has been performed on La 2 NiO 4+δ and La 2 CoO 4−δ . Experimental spectra at low temperatures provided an evidence for the existence of antiferromagnetic ordering in both of them. The internal field at La site in La 2 NiO 4+δ (19.3 kOe, ∥ c-axis) and in La 2 CoO 4−δ (30.5 kOe, ∥ c-axis) was significantly large comparing with that in La 2 CuO 4−δ (1.0 kOe 1 ⊥ c-axis), suggesting an importance of exchange interactions via apex oxygen atoms.