The oxygen-isotope effect on the in-plane penetration depth in underdoped Y1−x Prx Ba2 Cu3 O7−δ as revealed by muon-spin rotation

The oxygen-isotope (16O/18O) effect (OIE) on the in-plane penetration depth λab (0) in underdoped Y1−x Prx Ba2 Cu3 O7−δ was studied by means of muon-spin rotation. A pronounced OIE on λab−2 (0) was observed with a relative isotope shift of Δλab−2 /λ ab−2 = −5(2)% for x = 0.3 and −9(2)% for x = 0.4. The OIE exponents of Tc and of λab−2 (0) exhibit a relation that appears to be generic for cuprate superconductors.