Spin susceptibility behaviour in the Bi2Sr2Can−1CunO2n+4 compounds : from underdoped to overdoped regime

Abstract We have studied the thermal behaviour of the spin susceptibility, χ spin (T), of the CuO 2 planes in the normal phase. χ spin (T) was measured by 17 O and 43 Ca NMR in various compounds of the Bi 2 Sr 2 Ca n −1 Cu n O 2 n +4 family : a n=3 sample almost optimally doped, an overdoped n=2 sample and a more strongly doped n=1 sample. By contrast to the underdoped case, in the overdoped one, χ spin (T) increases when cooling. Furthermore, this behaviour is enhanced by increasing the doping. χ spin (T) is compared to the macroscopic susceptibility behaviour. On the other hand, our results are consistent with a decrease of the number of charge carriers per copper plane for increasing n.