Journal of Alloys and Compounds 509 (2011) 7886–7890 Contents lists available at ScienceDirect Journal of Alloys and Compounds j our na l ho me p ag e: www.elsevier.com/locate/jallcom Exchange biasing in SFMO/SFWO double perovskite multilayer thin films Deepak Kumar, Davinder Kaur ∗ Functional Nanomaterials Research Laboratory, Department of Physics and centre of nanotechnology, IIT Roorkee, Roorkee 247667, Uttarakhand, India a r t i c l e i n f o Article history: Received 24 August 2010 Received in revised form 2 May 2011 Accepted 3 May 2011 Available online 10 May 2011 Keywords: Multilayer SQUID Exchange bias Microstructure Blocking temperature a b s t r a c t In the present study, we have studied the exchange bias interaction in ferromagnetic Sr 2 FeMoO 6 (SFMO)/antiferromagnetic Sr 2 FeWO 6 (SFWO) multilayer thin films deposited on single crystal LaAlO 3 substrates using KrF pulsed laser deposition technique. XRD pattern revealed that SFMO, SFWO and their multilayer thin films were highly oriented along the c-axis. The microstructure studied by atomic force microscopy was found to be uniform, fine, dense and homogenous in nature. The observed magnetization- temperature curves showed Neel temperature T N ∼ 37 K for SFWO and Curie temperature T C > 320 K for SFMO thin films. For multilayer, the field cooled magnetization–field curve was shifted horizontally and the direction of the horizontal shift is opposite to that of H FC , indicating an exchange bias effect. Exchange bias field H E was found to decrease with increase in temperature and approached to zero at blocking temperature. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Exchange bias effect between ferromagnetic (FM) and antifer- romagnetic (AFM) material was discovered in 1956 by Meiklejohn and Bean [1]. Although there has been some research in exchange bias of nanoparticles in the last decades, the bulk of exchange bias research remained focused mainly on thin film systems [2,3]. When a FM/AFM multilayer thin film is cooled through the Neel tem- perature (T N ) of antiferromagnetic material (T N less than T C , the curie temperature of the ferromagnetic material), the hysteresis loop of FM is now shifted or biased away from the origin. This shift is known as the exchange field (H E ), can be several hundreds Oer- sted in size. Antiferromagnetic layers are an important component of hard disk read heads and of non-volatile magnetic random access memory elements, MRAM. The effect of exchange bias at the inter- face between an antiferromagnetic (AFM) and a ferromagnetic (FM) layer expresses itself as a unidirectional pinning or anisotropy of the magnetization of the ferromagnet, and is utilized to fix the magne- tization in a magnetic reference layer in a spin-valve structure or a magnetic tunnel junction (MTJ), which consists of two ferromag- netic layers separated by a non-magnetic metal (spin-valve) or an insulator (MTJ) [4–12]. The ideal structure of double perovskite materials can be viewed as a regular arrangement of corner-sharing BO 6 and B ′ O 6 octa- hedra, alternating along the three direction of crystal, with A cation occupying the voids in between the octahedra. The crys- tal structure and physical properties of double perovskite oxides ∗ Corresponding author. E-mail address: dkaurfph@iitr.ernet.in (D. Kaur). (A 2 BB ′ O 6 ) depend considerably on the size and valences of A, B and B ′ cations. For instance, in Sr 2 FeMoO 6 compound, the local- ized and coupled Fe spins of the Fe–O–Mo–O–Fe network through Mo 4d conduction electrons, give rise to a metallic ferromagnetic (T C ∼ 420 K) ground state [13–16]. Interestingly in the same line Sr 2 FeWO 6 is an anti-ferromagnetic (AFM) insulator with a low Neel temperature (T N ∼ 37 K) as Fe–O–W–O–Fe network enhances super-exchange coupling [17–19]. The origin of such a different behavior is mainly due to the 2p(O)–5d(W) orbital hybridization in Sr 2 FeWO 6 compound, being stronger than the 2p(O)–4d(Mo) hybridization in Sr 2 FeMoO 6 compound [20], which in turn pushes the 5d(W) band toward higher energies producing an insulating ground state and thereby inhibiting the ferromagnetic interaction active in Sr 2 FeMoO 6 compound [21,22]. Both the FM SFMO and AFM SFWO compositions exhibit tetragonally distorted perovskite structure with lattice mismatch of about 0.8% and are chemically compatible. The small mismatch and the chemical compatibility between the FM and AFM layers allow the growth of epitaxial het- erostructures with almost atomically perfect interfaces. The main objective of the present study is to fabricate the high quality SFMO, SFWO and [SFMO (100 ˚ A)/SFWO (40 ˚ A)] 15 mul- tilayer thin films and to examine the effect of temperature on exchange bias. To the best of our knowledge, there is no report on SFMO/SFWO multilayer thin films in literature. The values of the exchange field H E and coercivity H C , as a function of temperature, were measured and the blocking temperature was found. 2. Experimental SFWO, SFMO and [SFMO (100 ˚ A)/SFWO (40 ˚ A)]15 were fabricated on single crys- talline LaAlO3 substrate using multitarget pulsed laser deposition technique (Excel instruments, India). In order to synthesize the multilayer structure, SFMO and SFWO 0925-8388/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2011.05.006