Indah Nurpriyanti Lecture of physics

We have been demonstrated the detection of Fe3O4 nanoparticles by using giant magnetoresistance (GMR) sensor based on multilayer and spin valve thin films by using in Wheatstone bridge. The thin films were fabricated by DC magnetron sputtering method. The structure of multilayer thin film is [Co (1,5 nm)/ Cu(1,0 nm)]20 and spin valve thin film is IrMn (10 nm) / CoFe (3 nm) / Cu (2.2 nm) / CoFeB (10 nm). The Fe3O4 nanoparticles was synthesized by chemical coprecipitation method. The nanoparticles show superparamagnetic properties which saturation magnetization of 77 emu/gram and average particle size of 10 nm. The structure cystal of Fe3O4 magnetic nanoparticles was invers spinel. The output voltage of Wheatstone bridge is linear to the Fe3O4 concentrations (0.1 mg/ml; 1 mg/ml; 10 mg/ml; 100 mg/ml). That gradient was 0.20 for spin valve thin film and 0.07 for multilayer thin film. The gradient shows that spin valve thin film more sensitive than multilayer. The magnetic moment of spin valve thin film was saturated easier than multilayer thin film. The magnetization of spin valve thin film could be saturated by external field of 20 Oe, while multilayer was 5000 Oe. Magnetoresistance of spin valve was 6% and magnetoresistance of multilayer was 4%.

The main problem of the Indonesian people is that land is increasingly depleted with the increasing population of Indonesia. This will create problems for agriculture, because so far Indonesian citizens have used land as the main planting medium. Because of that, there were some breakthroughs in agriculture using planting media other than land, which is also called hydroponics. Of course this hydroponic has several drawbacks, one of which is the need for fairly complex maintenance. One difficulty is controlling the temperature and humidity in the environment. Therefore, in this study, the DHT11 sensor will be used as a temperature and humidity sensor for hydroponics based on Arduino uno R3 on water spinach plants. The steps that are made are (1) design design process (2) hydroponic design process (3) hydroponic manufacture (5) sensor design (6) testing. After the DHT11 sensor can detect temperature and humidity, the Arduino uno R3 will give commands to the water pump and the lights to turn on. The command is if the indicated temperature is less than 28oC then the fluorescent light will turn on. If the humidity is less than 76%, the water pump will run. After the experiment, the results obtained by the pump and lamp can be lit according to the command.