Spintronic devices, -based on the domain walls and skyrmions, Spintronic devices have shown significant potential for applications in energy-efficient data storage and beyond CMOS computing architectures. Based on the magnetic multilayer spintronic devices, we demonstrate the magnetic field-gated and current-controlled Leaky integrate and fire neuron characteristics for the spiking neural network applications. The LIF characteristics are controlled by the current pulses, which drive the domain wall motion, and an external magnetic field is used as the bias to tune the firing properties of the neuron. Thus, the device works like a gate-controlled LIF neuron, acting like a spintronic Mem-transistor device. The current and magnetic field-controlled neuron spiking rate is shown. We developed a LIF neuron model based on the measured characteristics to show the device's integration in the system-level SNNs. We extend the study and propose a scaled version of the demonstrated device with a multilayer spintronic domain wall magnetic tunnel junction as a LIF neuron. using the combination of SOT and the variation of the demagnetization energy across the thin film, the modified leaky integrate and fire LIF neuron characteristics are realized in the proposed devices. Finally, we integrate the measured and simulated neuron models in the 3-layer spiking neural network (SNN) and convolutional spiking neural network CSNN framework to test these spiking neuron models for classification of the MNIST and FMNIST datasets. In both architectures, the network achieves classification accuracy above 96%. Considering the good system-level performance, mem-transistor properties, and promise for scalability. The presented devices show an excellent alternative for neuromorphic computing applications.