Magnetic susceptibility above Tc: Connections with oxygen order in the CuO1−δ plane

Susceptibility experiments performed in the normal phase of YBa 2 Cu 3 O 7−δ for different values of δ show striking differences to the method of preparation of samples. Two main classes of samples can be found with two different types of susceptibilities which we ascribe to different ordering of oxygens in Cu(1) planes.