[Paper Review] Dilute magnetic semiconductor and half-metal behaviour mediated by 3d transition-metal doped in black/blue phosphorene

Weiyang Yu, Zhili Zhu+4 more|arXiv (Cornell University)|Apr 7, 2015

2D Materials and Applications1 citations

TL;DR

This study uses first-principles density-functional theory to investigate 3d transition metal (TM) doping in black and blue phosphorene, revealing that Ti, V, Cr, Mn, Fe, and Ni dopants induce dilute magnetic semiconductor (DMS) behavior in both phases, while Ti and Ni in blue phosphorene exhibit half-metallic properties. The magnetic behavior arises from partially filled non-bonding d states, with Sc and Co dopants remaining nonmagnetic due to fully occupied bonding states.

ABSTRACT

We present first-principles density-functional calculations for the structural, electronic, and magnetic properties of substitutional 3d transition metal (TM) impurities in two-dimensional black and blue phosphorenes. We find that the magnetic properties of such substitutional impurities can be understood in terms of a simple model based on the Hund's rule. The TM-doped black phosphorenes with Ti, V, Cr, Mn, Fe and Ni impurities show dilute magnetic semiconductor (DMS) properties while those with Sc and Co impurities show nonmagnetic properties. On the other hand, the TM-doped blue phosphorenes with V, Cr, Mn and Fe impurities show DMS properties, those with Ti and Ni impurities show half-metal properties, whereas Sc and Co doped systems show nonmagnetic properties. We identify two different regimes depending on the occupation of the hybridized electronic states of TM and phosphorous atoms: (i) bonding states are completely empty or filled for Sc- and Co-doped black and blue phosphorenes, leading to non-magnetic; (ii) non-bonding d states are partially occupied for Ti-, V-, Cr-, Mn-, Fe- and Ni-doped black and blue phosphorenes, giving rise to large and localized spin moments. These results provide a new route for the potential applications of dilute magnetic semiconductor and half-metal in spintronic devices by employing black and blue phosphorenes.

Motivation & Objective

• To investigate the structural, electronic, and magnetic properties of 3d transition metal impurities in two-dimensional black and blue phosphorene.
• To determine the conditions under which these doped systems exhibit dilute magnetic semiconductor (DMS) or half-metallic behavior.
• To establish a physical model explaining the magnetic behavior based on Hund's rule and hybridized electronic states.
• To identify promising candidates for spintronic devices by analyzing spin moment localization and electronic structure.

Proposed method

• First-principles density-functional theory (DFT) calculations were performed to analyze the electronic and magnetic properties of substitutional 3d transition metal dopants in black and blue phosphorene.
• The study examined the occupation of hybridized electronic states between transition metal d-orbitals and phosphorus p-orbitals to classify bonding and non-bonding character.
• Spin-polarized calculations were used to determine the presence and magnitude of localized spin moments in doped systems.
• The analysis focused on distinguishing between systems with completely filled or empty bonding states (nonmagnetic) and those with partially filled non-bonding d states (magnetic).
• The magnetic behavior was interpreted using a model based on Hund's rule, emphasizing electron correlation effects in d-orbitals.
• Comparative analysis between black and blue phosphorene phases was conducted to assess structural and electronic differences induced by doping.

Experimental results

Research questions

• RQ1 Which 3d transition metal dopants induce dilute magnetic semiconductor (DMS) behavior in black and blue phosphorene?
• RQ2 What electronic structure features differentiate nonmagnetic systems from magnetic ones in TM-doped phosphorenes?
• RQ3 Why do Ti and Ni dopants in blue phosphorene exhibit half-metallic behavior while others show DMS or nonmagnetic states?
• RQ4 How does the hybridization between transition metal d-orbitals and phosphorus p-orbitals influence the magnetic and electronic properties?
• RQ5 Can a simple model based on Hund's rule explain the observed magnetic moments in doped phosphorenes?

Key findings

• Ti, V, Cr, Mn, Fe, and Ni dopants in black phosphorene exhibit dilute magnetic semiconductor (DMS) behavior due to partially filled non-bonding d states.
• Sc and Co dopants in black phosphorene remain nonmagnetic because their bonding states are completely filled.
• In blue phosphorene, V, Cr, Mn, and Fe dopants show DMS behavior, while Ti and Ni exhibit half-metallic character with a gap in the spin-down channel.
• Sc and Co dopants in blue phosphorene are nonmagnetic, consistent with fully occupied bonding states.
• The magnetic moments in DMS and half-metallic systems arise from localized, partially filled non-bonding d states, in line with Hund's rule.
• The distinction between nonmagnetic and magnetic behavior is determined by the occupation of hybridized electronic states: filled/empty bonding states lead to nonmagnetism, while partially filled non-bonding states lead to large, localized spin moments.