IOP PUBLISHING JOURNAL OF PHYSICS D: APPLIED PHYSICS J. Phys. D: Appl. Phys. 40 (2007) 7565–7571 doi:10.1088/0022-3727/40/23/049 Internal friction and longitudinal modulus behaviour of multiferroic PbZr 0.52 Ti 0.48 O 3 +Ni 0.93 Co 0.02 Mn 0.05 Fe 1.95 O 4-δ particulate composites M Venkata Ramana 1 , G Sreenivasulu 2 , N Ramamanohar Reddy 1 , K V Siva Kumar 1 , B S Murty 2 and V R K Murthy 3 1 Ceramic Composite Materials Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur–515 003, India 2 Nanotechnology Laboratory, Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Chennai–600 036, India 3 Microwave Laboratory, Department of Physics, Indian Institute of Technology, Chennai-600 036, India E-mail: sivakumar.sivani@gmail.com Received 30 August 2007, in final form 5 October 2007 Published 16 November 2007 Online at stacks.iop.org/JPhysD/40/7565 Abstract Multiferroic particulate composites with composition x Ni 0.93 Co 0.02 Mn 0.5 Fe 1.95 O 4−δ + (1 − x)PbZr 0.52 Ti 0.48 O 3 where the molar fraction x varies as 0, 0.1, 0.2, 0.3, 0.4 and 0.5 were prepared by the conventional ceramic method. The presence of two phases was confirmed by x-ray diffraction and scanning electron microscopy. The temperature variation of the longitudinal modulus (L) and the internal friction (Q −1 ) of these particulate composites at 104.387 kHz was studied in the wide temperature range 30–420 ◦ C. The temperature variation of the longitudinal modulus (L) in each composition of these particulate composites showed two abrupt minima. One minimum coincided with the ferroelectric–paraelectric Curie transition temperature (θ E ) and the other with the ferrimagnetic–paramagnetic Curie transition (θ M ) temperature. The internal friction (Q −1 ) measurements also showed two sharp peaks in each composition corresponding to those temperatures where the minima were noticed in the temperature variation of the longitudinal modulus behaviour. The Curie transition temperature of pure ferrite was found to be 560 ◦ C. Addition of 10% of ferrite to ferroelectric in a magnetoelectric (ME) composite resulted in a 360 ◦ C fall in θ M and with a further increase in ferrite content the θ M variation was found to be very nominal. However, no significant ferroelectric Curie transition temperature shift could be noticed. This behaviour is explained in the light of structural phase transitions in these multiferroic particulate composites. These ME composites were prepared with a view to using them as ME sensors and transducers. 1. Introduction Composite materials consisting of piezoelectric and piezomagnetic phases show a magnetoelectric (ME) effect. The ME effect is a coupled, two field effect, in which the application of electric field induces magnetization and the magnetic field produces an electric polarization. The ME effect is a property of the composites which is absent in their constituent phases [1]. When a magnetic field is applied to an ME composite containing both piezoelectric and 0022-3727/07/237565+07$30.00 © 2007 IOP Publishing Ltd Printed in the UK 7565