Magnetic phase diagram of Ge1–x–y(SnxMny)Te multiferroic semiconductors: Coexistence of ferromagnetic and cluster glass ordering

Abstract

Noncentrosymmetric IV-VI semiconductors doped with magnetic ions offer exciting possibilities such as carrier mediated ferromagnetism, ferroelectric-controlled spin texture and integration of semiconducting features with ferromagnetic order. Also, coupling between more than one ferroic orders and giant Rashba spin splitting can be studied to develop materials for spintronic applications. In that context, we report the structural and magnetic results of polar α–GeTe doped with Sn and Mn from x = 0.185–0.841 and y = 0.02–0.086, respectively. The magnetic results of Ge1–x–y(SnxMny)Te (GSMT) crystals identify Mn-clustering effect with scaling parameter, R = 0.033 for x ≈ 0.2 and y = 0.06. The excessive Sn ions are assumed to drive the inception of short range ferromagnetic clusters. For the crystals revealing glassy magnetic behavior, the irreversibility temperature, Tirr shifts at high dc magnetic field which is well described by de Almeida-Thouless equation, δTirr ∝ HΦ/2 yielding Φ values of 1.55 and 1.7 that validates the formation of Mn clusters. The spin relaxation time, τ0 ∼ 10–9 s, activation energy, Ea/kB ∼ 5 TF where TF is freezing temperature and Vogel-Fulcher temperature, T0 ∼ TF also signify intracluster interactions. Also, the Mn-hole magnetic exchange constant, Jpd drops from 0.24 eV for the samples with smaller Sn content of x ≈ 0.2 to 0.16 eV for Sn rich alloy with x ≈ 0.8. Consequently, we present a magnetic phase diagram for GSMT bulk crystals as a function of Mn ions.