[Paper Review] Enhanced Spin Lifetime and Long-Range Spin Transport in p-Silicon using Spin Gapless Semiconductor as Ferromagnetic Injector

Nilay Maji, Subham Mohanty+2 more|arXiv (Cornell University)|Feb 13, 2026

Heusler alloys: electronic and magnetic properties0 citations

TL;DR

Demonstrates electrical spin injection, accumulation, and transport in lightly doped p-type silicon using Mn2CoAl as a spin injector, achieving measurable spin lifetimes and long-range diffusion.

ABSTRACT

Electrical spin injection and transport in silicon are central challenges for realizing semiconductor-based spintronic devices, particularly in p-type Si, where strong spin relaxation and interface effects often suppress detectable spin signals. Here, we report electrical spin injection, accumulation, and transport in lightly doped p-type silicon using the spin-gapless Heusler compound Mn$_2$CoAl as a ferromagnetic spin injector, separated from the p-Si channel by a thin MgO tunnel barrier in a lateral device geometry. Spin transport is systematically investigated through three-terminal (3-T) Hanle and four-terminal (4-T) nonlocal (NL) spin-valve and Hanle measurements. Clear Lorentzian Hanle signals are observed in the 3-T configuration from 5 K up to room temperature, yielding a spin lifetime of $\sim$0.68 ns at 300 K that increases to $\sim$4.11 ns at 5 K. Temperature-dependent analysis reveals a weak power-law dependence of the spin lifetime, indicating Bir--Aronov--Pikus--type spin relaxation mechanism. To validate genuine spin transport, NL spin-valve and Hanle measurements were performed, revealing well-defined spin-valve switching and controlled spin precession at 5 K. From NL Hanle fitting, a spin lifetime of $\sim$5.65 ns and a spin diffusion length of $\sim$0.82 $μ$m are extracted, confirming diffusive long-range spin transport in the p-Si channel. Although NL signals diminish at elevated temperatures due to reduced interfacial spin polarization and thermal noise, the combined 3-T and 4-T results establish spin-gapless Mn$_2$CoAl as an effective spin injector for p-type silicon. These findings highlight the potential of spin-gapless semiconductors for improving spin injection efficiency and advancing Si-compatible spintronic devices.

Motivation & Objective

• Motivate and enable electrical spin injection and transport in p-type silicon where relaxation is strong and interfaces hinder signals.
• Use a spin-gapless semiconductor (Mn2CoAl) as a ferromagnetic injector to improve spin injection efficiency into p-Si.
• Characterize spin lifetime, diffusion length, and transport mechanism through 3-terminal Hanle and nonlocal measurements across temperatures.
• Validate genuine spin transport via combined three-terminal and four-terminal measurements showing spin-valve behavior and controlled precession.

Proposed method

• Fabricate a lateral device with Mn2CoAl as the ferromagnetic injector separated from a lightly doped p-Si channel by a thin MgO tunnel barrier.
• Perform three-terminal (3-T) Hanle measurements to detect Lorentzian spin signals from 5 K to 300 K.
• Perform four-terminal (4-T) nonlocal (NL) spin-valve and Hanle measurements to extract spin lifetime and diffusion length via NL Hanle fitting.
• Analyze temperature dependence of spin lifetime to identify the dominant spin relaxation mechanism (Bir–Aronov–Pikus–type).
• Extract spin lifetime and diffusion length from NL data to confirm diffusive long-range spin transport in p-Si.

Experimental results

Research questions

• RQ1 Can spin-gapless semiconductors efficiently inject spins into p-type silicon through a tunnel barrier?
• RQ2 What are the spin lifetime and diffusion length in lightly doped p-Si when using Mn2CoAl as injector across a temperature range?
• RQ3 Does three-terminal Hanle and four-terminal nonlocal measurements provide consistent evidence of spin transport in p-Si?
• RQ4 What is the dominant spin relaxation mechanism in this system?
• RQ5 How does interfacial spin polarization and thermal noise affect spin signals at elevated temperatures?

Key findings

• 3-T Hanle signals are observed from 5 K to 300 K, yielding a spin lifetime of ~0.68 ns at 300 K and ~4.11 ns at 5 K.
• NL spin-valve and Hanle measurements show well-defined spin switching and spin precession at 5 K.
• NL Hanle fitting yields a spin lifetime of ~5.65 ns and a spin diffusion length of ~0.82 μm, confirming diffusive long-range spin transport in p-Si.
• Spin lifetime shows weak power-law temperature dependence consistent with Bir–Aronov–Pikus–type relaxation.
• Signals diminish at higher temperatures due to reduced interfacial spin polarization and thermal noise, but 3-T and 4-T data collectively validate spin-gapless Mn2CoAl as an effective spin injector for p-type silicon.