Unusual exchange bias in Sr₂FeIrO₆/La_0.67Sr_0.33MnO₃ multilayer

Abstract

Here, we study interface induced magnetic properties in a 3d-5d based multilayer made of La0.67Sr0.33MnO3 and double perovskite Sr2FeIrO6, respectively. Bulk La0.67Sr0.33MnO3 is metallic and shows ferromagnetic (FM) ordering above room temperature. In contrast, bulk Sr2FeIrO6, is an antiferromagnet (AFM) with a Néel temperature around 45 K () and exhibits an insulating behavior. Two set of multilayers have been grown on SrTiO3 (1 0 0) crystal with varying thickness of FM layer. A multilayer with equal thickness of La0.67Sr0.33MnO3 and Sr2FeIrO6 (∼10 nm) shows exchange bias (EB) effect both in conventionally field cooled (FC) as well as in zero field cooled (ZFC) magnetic hysteresis measurements which is rather unusual. The ZFC EB effect is weakened both with increasing maximum field during initial magnetization process at low temperature and with increasing temperature. Interestingly, a multilayer with reduced thickness of La0.67Sr0.33MnO3 (∼5 nm) does not exhibit ZFC EB phenomenon, however, the FC EB effect is strengthened showing much higher value. We believe that an AFM type exchange coupling at the interface and its evolution during initial application of magnetic field causes this unusual EB in present multilayers.

Low temperature ferromagnetism in perovskite SrIrO$_3$ films

“…In order to maintain the oxygen stoichiometry, the deposited films have been post annealed at same deposition temperature 750 • C for about 15 min at partial oxygen pressure around 500 mbar. The thickness of the films has been estimated using calibrated laser shot counts 29 which closely matches with the thickness checked with FESEM. The structural characterization of the films are performed with x-ray diffraction (XRD) where the data have been collected using a Panlytical diffractometer equipped with Cu-K α source.…”

“…40 The applied field biases the exchange interaction at interface which results in a shifting of M (H) plot or EB phenomena. 24,29,43 However, the interfaces in films or multilayers experience various other factors, such as structural distortion, electronic reconstruction, strain, etc. which modify the magnetic characters at interface accordingly.…”

“…41,42 These in turn induces EB effect which has shown many many interesting properties. For instance, EB effect has been observed even in zero-field-cooled M (H) plot 24,29 and in single-layer magnetic films, 44 which are rather unusual. The observed EB effect in present single layer SrIrO 3 , deposited on diamagnetic SrTiO 3 , is likely due to strain effect.…”

Structural, magnetic and dielectric properties in 3$d$-5$d$ based Sr$_2$FeIrO$_6$ thin films

“…Thickness of films has been determined from laser shot calibration, details are given elsewhere. [46] For dielectric measurement first ∼ 15 nm thick La 0.67 Sr 0.33 MnO 3 (LSMO) film has been deposited on SrTiO 3 (100) substrate. The system is then cooled to room temperature, and a small mask has been used on a small portion of deposited LSMO film where subsequently ∼ 25 nm Sr 2 FeIrO 6 and ∼ 15 nm LSMO films have been grown following above mentioned parameters (see Figure 1e).…”

“…Two AFM transitions, a sharp transition around 45 K and a weak transition around 120 K have been seen in bulk Sr 2 FeIrO 6 magnetization data. [20] The onset of AFM ordering appears to start around 120 K which becomes prominent at ∼ 45 K. [20] The low temperature AFM ordering around 45 K is even preserved in magnetization data for (Sr 2 FeIrO 6 /La 0.67 Sr 0.33 MnO 3 ) 3 multilayer which has shown interesting exchange bias effect below 45 K. [46] The temperature dependent magnetization M(T ) data for singlelayer thin films collected following zero field cooled (ZFC) and field cooled (FC) protocol have been shown in Figure 5. For collection of M(T ) data, the magnetic field has been used as 1000 Oe for 60 nm film (Figure 6c) and 100 Oe for 40, 25 nm thick film (Figures 6b and 6a).…”