**1. Introduction**

Current semiconductor-based electronics device uses only the electron charging property to perform a particular feature in which the electron spin degree is completely ignored [1]. The spin property of an electron which is associated with an intrinsic angular momentum of the electron provides new effects and new functionalities to electronics materials based on Spintronics principle [2, 3]. Spintronics deals with the role played by the spin of an electron associated with its magnetic moment, as well as the charge degree of electron [4]. Spintronics devices have several important applications compared to non-spin based electronics device, such as consume

**Figure 1.**

*Schematic view of a non-magnetic (left) semiconductor and a diluted magnetic semiconductor (right) [5].*

less power of electricity, fast data processing speed, their memories are non-volatile [4]. Starting from metal-based technology, the research area of Spintronics shifted to the recent development of diluted magnetic semiconductors (DMS) materials which are compatible with standard semiconductor based electronics device**.** DMS are materials prepared through which a certain amount of the cations in a host semiconductor are partially replaced by transition metal ions (Mn, Ni, Co, Fe, Cr) as shown in **Figure 1** [5] as a result the materials attains both semiconducting and magnetic property which is makes these materials advantageous and applicable for Spintronics application. The total ferromagnetic behavior of these materials is linked to the interaction of the spin of the magnetic ions with the itinerant carriers [6–8]. DMS are important materials in the sense that logic, communications and storage operation can be achieved within the same materials technology [9, 10]. The property of achieving RTFM is one of the most important factors that determined DMS material to be used for practical spintronics application [7], The sp-d exchange mechanism between the d states of the TM doping and sp free carriers as well as the double exchange mechanisms are the main factor in the production of ferromagnetism in ODMS materials between d states of TM ions [11]. Among DMS materials oxide based DMS materials such as TM doped with HfO2, TiO2, ZnO and SnO2 are more advantageous than normal DMS materials and have important magnetic properties arises from a large sp-d exchange interactions between the magnetic ion elements and band electrons [9, 10, 12, 13]. ODMS has important special properties such as having high n-type carrier concentrations wide band gap, light transparency, capability to be grown at low temperatures, ecological safety and cheap [14–16]**.** Due to its n-type semiconductor, good conductivity, high carrier density and high chemical stability, SnO2 doped with TM is particularly promising materials for spintronic applications [17, 18]**.** SnO2 naturally existing in cassiterite form and it has tetragonal rutile structure and its wide band gap is about 3.6 eV [19, 20]. SnO2 has many technological applications, including gas sensors, solar cells, heat reflectors, lithium ion batteries and other optoelectronic devices [21–23].

## **2. Ferromagnetism in oxide-based DMS**

In the recent years the research field of RTFM in O-DMS has got more attention and many kinds of compounds have been discovered [24]. However, the idea behind the original source of ferromagnetism in these materials is not well understood a not complete it becomes the most challenging area in solid state physics [25]. Several groups have stated that the mechanism behind ferromagnetism in most O-DMS materials is the material's intrinsic property itself or the direct and indirect

**135**

**Figure 2.**

*M-H curves of (Ni-Mn) co-doped with SnO2 [11].*

*Ferromagnetism in SnO2 Doped with Transition Metals (Fe, Mn and Ni) for Spintronics…*

interaction between only magnetic impurities and magnetic impurity ions through oxygen vacancies [10, 26–30]. Recently, various experimental methods have been used to study the magnetic properties of DMS materials, in particular the vibrating sample magnetometer (VSM), the superconducting quantum interference device (SQUID), the physical property measurement system (PPMS) and the electron spin resonance (ESR) techniques. According to the results from many literature indicated that sample preparation, growth conditions, dopant type and concentration, co-doping effect, oxygen vacancies, defects and crystal structure has played a role for the magnetic behaviors observed in ODMS material [31–37]**.** Some scholars reported that vacancy-induced magnetism has been played a major role for the observed ferromagnetism in undoped SnO2 [38]. In some cases SnO2 thin films does not shows RTFM when doped with 3*d* cations rather show when doped with Mn, Cr, Fe, Co, or Ni [39–41]. Similarly undoped SnO2 did not shows FM behavior. However, the doped SnO2 shows FM behavior at higher doping level completely removes the ferromagnetic behavior of the doped one [31, 42]**.** As shown in **Figure 2** the improvement of magnetization by co doping (Ni-Mn, Fe-Co, Fe-Ni and Fe-Mn) in tin oxide has been reported and the mechanism of FM is due to double exchange interactions occur via oxygen vacancies [11, 43]. The electronic or lattice defects of the materials associated with the intrinsic nature of the materials can be responsible for the high temperature FM of TM doped SnO2 [39]. Despite much experimental success, the idea behind FM in most O-DMS is controversial. Here, we present a brief review of the Fe, Ni and Mn Doped SnO2 system experimental work.

Mn-doped SnO2 is an excellent candidate and promising materials for RTFM study, but only very little work has been reported so far compared to others. Among other preparation methods sol-gel preparation technique is best method for prepa-

SnMnO2 thin film is prepared by sol-gel method according to the literature reported [44]. The solution was prepared by dissolving a certain amount of tin tetrachloride SnCl4 and manganese nitrate hydrate [Mn (NO3)26H2O] in distilled water and

ration of TM doped SnO2 thin film and nano structures [44, 45].

*DOI: http://dx.doi.org/10.5772/intechopen.90902*

**2.1 Ferromagnetism in Mn-doped SnO2**

*2.1.1 Experimental*

*Ferromagnetism in SnO2 Doped with Transition Metals (Fe, Mn and Ni) for Spintronics… DOI: http://dx.doi.org/10.5772/intechopen.90902*

interaction between only magnetic impurities and magnetic impurity ions through oxygen vacancies [10, 26–30]. Recently, various experimental methods have been used to study the magnetic properties of DMS materials, in particular the vibrating sample magnetometer (VSM), the superconducting quantum interference device (SQUID), the physical property measurement system (PPMS) and the electron spin resonance (ESR) techniques. According to the results from many literature indicated that sample preparation, growth conditions, dopant type and concentration, co-doping effect, oxygen vacancies, defects and crystal structure has played a role for the magnetic behaviors observed in ODMS material [31–37]**.** Some scholars reported that vacancy-induced magnetism has been played a major role for the observed ferromagnetism in undoped SnO2 [38]. In some cases SnO2 thin films does not shows RTFM when doped with 3*d* cations rather show when doped with Mn, Cr, Fe, Co, or Ni [39–41]. Similarly undoped SnO2 did not shows FM behavior. However, the doped SnO2 shows FM behavior at higher doping level completely removes the ferromagnetic behavior of the doped one [31, 42]**.** As shown in **Figure 2** the improvement of magnetization by co doping (Ni-Mn, Fe-Co, Fe-Ni and Fe-Mn) in tin oxide has been reported and the mechanism of FM is due to double exchange interactions occur via oxygen vacancies [11, 43]. The electronic or lattice defects of the materials associated with the intrinsic nature of the materials can be responsible for the high temperature FM of TM doped SnO2 [39]. Despite much experimental success, the idea behind FM in most O-DMS is controversial. Here, we present a brief review of the Fe, Ni and Mn Doped SnO2 system experimental work.
