Research Interests

MAGNETIC & ADVANCED CERAMICS LAB was set up to pursue research with the basic theme of “Magnetic, Electronic and other Ferroic properties of solids”.

Areas of research being pursued in the lab fall in the category of : Novel Functional Ferroic Materials

Ø  Topological Insulators

Ø  Magnetoelectric multiferroic materials

Ø  Magnetic shapememory in Heusler alloys

Ø  Shape memory in ceramics

Ø  Micowave absorbing materials

Ø  Magnetic ion doped high-k oxides

 In recent years, there has been a surge of research interest in smart multifunctional / active materials. ‘Smart Materials’, very useful in technology applications are those that change the coefficient of one of their properties (shape/ electrical signal/ magnetic signal/ optical signal) in response to an external stimulus (temperature/ stress/ applied fields etc.) and this change in (shape/ electrical signal/ magnetic signal/ optical signal) can be used to control the stimulus itself.

In technology, such materials can be used for sensing and actuation simultaneously. Historically, piezoelectric/ magnetostrictive/ shape-memory alloys like Nitinol have been used for such purpose. For these, electric field/ magnetic field/ temperature (respectively) were the driving external stimulus; with unique functionality for each sensor or actuator. The recent interests of researchers are to develop materials with multiple functionality.

 1.  Magnetoelectric Multiferroic Materials- Multiferroic materials are those that possess more than one ferroic properties that are coupled. Usually broad transitions in dielectric spectra are observed in many of these multiferroic candidates that are reported in literature either as relaxor ferroelectrics with frustrated ferroelectricity or are explained on the basis of Maxwell-Wagner capacitor model that suggests that the observed relaxation and dielectric enhancement may be the artefacts of space charge contributions. An important issue faced by the researchers in the field is thus to establish the origin of broad transitions usually observed in dielectric spectra.

       In the lab we are working on both ‘solid-solution multiferroic materials’ and ‘multiferroic composites’.

2.  Ferromagnetic Shape Memory Alloys (FSMA) – These are potential new class of actuator materials that show magnetic field-induced strain in the ferromagnetic martensite phase. Magnetic field induced strains of 6% to 10% in Ni-Mn-Ga martensites have been reported at room temperature. These strains are the result of twin-boundary motion: twin variants of martensite can be reoriented or aligned by an external magnetic field or stress. Ni-Mn-Ga  FSMA is able to respond at higher frequencies (up to at least 300Hz) with comparable strains (up to several %) in a moderate field of 1 Tesla. By way of comparison, piezoelectric materials show strains of the order of ~0.1 % and the leading magnetostrictive material, Terfenol-D shows a field-induced strain of ~ 0.24 % .

       We have completed and have ongoing national /international projects in this field of research and have published several research papers (references 1-7) in international journals of repute.

 3.   Shape Memory Ceramics - Piezoelectric materials show induced strain on application of electric field, which normally disappears after the removal of electric field. However, if in a sample this field induced strain remains even after the removal of electric field and a small electric field in opposite direction is required to bring the sample back to its original shape, it is called shape memory ceramics. In these ceramic materials, stress, temperature or electric field-induced antiferroelectric (AFE) to ferroelectric (FE) phase transition is responsible for shape memory effect. An important difference between shape memory ceramics and FSMA and metallic shape memory alloys lie in their comparative band-widths. The band-widths of ceramic materials are ~ 100 kHz, leading to quick response-time; in comparison, the metallic shape memory alloys show comparatively much smaller band-width ~ 100Hz. Thus, although remnant strain is quite small in shape memory ceramics, their small response time, high durability and less power consumption are expected to be the positive features making them more attractive for industrial use.

                   We have studied lead based system [(Pb(ZrSnTi)O3] for exact morphotropic phase boundary and further this exact MPB composition is modified at A-site and B-site for better shape memory effect. We are also working on lead free ceramics for shape memory effect.

4.    Microwave Absorbing Materials - Microwave absorbers and reflectors have long been in use, in both civil and military applications, on account of their ability to reduce electromagnetic wave pollution and decrease radar signatures. Recently, the demand for microwave absorbing material has increasingly grown because of its three-fold application in electromagnetic interference (EMI) shielding of electronic equipment, for protection of humans from adverse effects of EM radiation and counter measures to radar detection, i.e. stealth technology.  In our lab, we develop materials that absorb microwave in the range 8-12 GHz .

 5.    Magnetic ion-doped high-k oxides - In recent years high-k dielectric oxides are being investigated extensively as gate dielectrics for next generation devices in semiconductor technology. In view of the material compatibility with Si, if such oxides can also respond magnetically, they can be used for spintronic applications.

         In our lab we work on high k- oxides like (HfO₂, ZrO₂, ZnO) that are doped by transition metal elements using an alternative, highly versatile method of using ion-implantation into these oxide thin films. Compared to molecular beam epitaxy and pulsed laser deposition (PLD) techniques, our synthesis approach has fewer restrictions on the choice of host material and alloying species. Any element can be injected into a solid in a controlled and reproducible manner by ion implantation. This doping process is nonequilibrium in nature- a feature that often leads to the formation of compositions and structures that cannot be obtained by conventional processing methods.